如何在没有内存复制的情况下在 OpenGL 中旋转 Cubemap 面？
How to rotate Cubemap face without memory copy in OpenGL?
问题更新：
在前面的问题描述中，我犯了几个严重的错误，导致问题很难理解和解决。现在我将分享我最新的有效代码。
我之前对每个面的方向的描述是错误的。正确的方向是这样的：
右面顺时针旋转90度，顶面顺时针旋转180度
所以在设置由两个三角形（3-7-8和8-4-3）组成的右脸的纹理坐标时，我们需要将脸逆时针旋转90度，所以3 将使用 7 的坐标，7 -> 8, 8 -> 4, 4 -> 3。为由两个三角形（1-4-8 和 8-6-1）组成的顶面设置纹理坐标时，我们需要将脸逆时针旋转90度，所以1会用到8的坐标，4 -> 6, 8 -> 1, 6 -> 4.
有效代码：
bool setupCoordinates() {
this->vertexCount = 36;
float skyboxVertices[] = {
// positions
// back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
float skyboxTextures[] = {
// positions
// Back same as skyboxVertices
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left same as skyboxVertices
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right rotate in 90 ccw
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
// Front same as skyboxVertices
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top rotate in 180 ccw
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
// Bottom same as skyboxVertices
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
glGenVertexArrays(1, &sceneVAO);
glBindVertexArray(sceneVAO);
glGenBuffers(1, &sceneVertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, sceneVertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glGenBuffers(1, &sceneUVBuffer);
glBindBuffer(GL_ARRAY_BUFFER, sceneUVBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxTextures), &skyboxTextures, GL_STATIC_DRAW);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glBindVertexArray(0);
return true;
}
void drawFrame() {
glBindTexture(GL_TEXTURE_CUBE_MAP, sceneTextureID);
glPixelStorei(GL_UNPACK_ROW_LENGTH, videoFrameWidth);
int width = videoFrameWidth / 3;
int height = width;
// back
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// left
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// front
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// bottom
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// right
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB,width,width,0,GL_RGB,GL_UNSIGNED_BYTE, textureData);
// top
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
}
-------------------------------------------- ---原题-------------------------------------------- ---
我有一个立方体贴图 3x2 格式的 360 视频，我想在 OpenGL 中使用立方体贴图纹理来渲染它。然而，立方体的背面和顶面在不同的方向旋转。背面顺时针旋转 90 度，顶面顺时针旋转 180 度。现在我可以通过内存复制正确渲染立方体贴图，但我想知道是否有办法通过使用 OpenGL 的内置功能来避免这种情况？
我需要渲染的帧：
顶点着色器：
#version 410 core
uniform mat4 matrix;
out vec3 TexCoords;
layout(location = 0) in vec4 position;
layout(location = 1) in vec3 textureIn;
void main() {
TexCoords = textureIn;
gl_Position = matrix * position;
}
片段着色器：
#version 410 core
varying vec3 TexCoords;
uniform samplerCube mytexture;
void main() {
gl_FragColor = texture(mytexture, TexCoords);
}
我用来渲染的代码：
void Player::SetupScene() {
this->m_sceneVertexCount = 36;
float skyboxVertices[] = {
// positions
// Back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
float skyboxTextures[] = {
// positions
// Back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
glGenVertexArrays(1, &m_SceneVAO);
glBindVertexArray(m_SceneVAO);
glGenBuffers(1, &m_sceneVertBuffer);
glBindBuffer(GL_ARRAY_BUFFER, m_sceneVertBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glGenBuffers(1, &m_sceneTexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, m_sceneTexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxTextures), &skyboxTextures, GL_STATIC_DRAW);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glBindVertexArray(0);
}
void Player::SetupTexture(unsigned char *textureData) {
int width = frameWidth / 3;
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
glBindTexture(GL_TEXTURE_CUBE_MAP, m_sceneTextureID);
// Render left face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render front face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render right face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render bottom face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Rotate the back face 90 degrees counter clockwise
uint8_t *start = textureData + rowLength * height * 3 + width * 3;
for (int j = 0; j < height; j++) {
for (int i = 0; i < width; i++) {
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 0] = *(start + i * 3 + 0);
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 1] = *(start + i * 3 + 1);
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 2] = *(start + i * 3 + 2);
}
start += rowLength * 3;
}
glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pRightFaceBuffer);
// Rotate the bottom face 180 degrees counter clockwise
start = textureData + rowLength * height * 3 + width * 2 * 3;
for (int j = 0; j < height; j++) {
for (int i = 0; i < width; i++) {
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 0] = *(start + (i) * 3);
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 1] = *(start + (i) * 3 + 1);
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 2] = *(start + (i) * 3 + 2);
}
start += rowLength * 3;
}
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pUpFaceBuffer);
}
我用来构建立方体贴图的坐标：
您可以通过glTexImage2D直接指定立方体贴图的边：
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
// Render left face
[...]
// Render front face
[...]
// Render right face
[...]
// Render bottom face
[...]
// Render back face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render top face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width*2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
但是您必须更改右侧和顶部的纹理坐标。请注意，您弄乱了立方体贴图边到立方体边的映射，但无论如何它都有效：
float skyboxTextures[] = {
// positions
// Back
// [...]
// Left
// [...]
// Right
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
// Front
// [...]
// Top
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
// Bottom
// [...]
};
查看结果：
由于侧面的映射似乎很乱，我更愿意像这样加载侧面：
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
// Render back face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render left face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render right face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render front face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render top face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width*2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render bottom face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
并使用以下纹理坐标：
float skyboxTextures[] = {
// positions
// Back
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
// Bottom
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f
};
但请注意，y 轴和 z 轴仍然互换。我假设这是因为场景中的世界 space 向上向量是 (0, 1, 0).
问题更新：
在前面的问题描述中，我犯了几个严重的错误，导致问题很难理解和解决。现在我将分享我最新的有效代码。
我之前对每个面的方向的描述是错误的。正确的方向是这样的：
右面顺时针旋转90度，顶面顺时针旋转180度
所以在设置由两个三角形（3-7-8和8-4-3）组成的右脸的纹理坐标时，我们需要将脸逆时针旋转90度，所以3 将使用 7 的坐标，7 -> 8, 8 -> 4, 4 -> 3。为由两个三角形（1-4-8 和 8-6-1）组成的顶面设置纹理坐标时，我们需要将脸逆时针旋转90度，所以1会用到8的坐标，4 -> 6, 8 -> 1, 6 -> 4.
有效代码：
bool setupCoordinates() {
this->vertexCount = 36;
float skyboxVertices[] = {
// positions
// back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
float skyboxTextures[] = {
// positions
// Back same as skyboxVertices
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left same as skyboxVertices
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right rotate in 90 ccw
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
// Front same as skyboxVertices
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top rotate in 180 ccw
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
// Bottom same as skyboxVertices
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
glGenVertexArrays(1, &sceneVAO);
glBindVertexArray(sceneVAO);
glGenBuffers(1, &sceneVertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, sceneVertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glGenBuffers(1, &sceneUVBuffer);
glBindBuffer(GL_ARRAY_BUFFER, sceneUVBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxTextures), &skyboxTextures, GL_STATIC_DRAW);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glBindVertexArray(0);
return true;
}
void drawFrame() {
glBindTexture(GL_TEXTURE_CUBE_MAP, sceneTextureID);
glPixelStorei(GL_UNPACK_ROW_LENGTH, videoFrameWidth);
int width = videoFrameWidth / 3;
int height = width;
// back
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// left
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// front
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// bottom
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// right
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB,width,width,0,GL_RGB,GL_UNSIGNED_BYTE, textureData);
// top
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
}
-------------------------------------------- ---原题-------------------------------------------- ---
我有一个立方体贴图 3x2 格式的 360 视频，我想在 OpenGL 中使用立方体贴图纹理来渲染它。然而，立方体的背面和顶面在不同的方向旋转。背面顺时针旋转 90 度，顶面顺时针旋转 180 度。现在我可以通过内存复制正确渲染立方体贴图，但我想知道是否有办法通过使用 OpenGL 的内置功能来避免这种情况？
我需要渲染的帧：
顶点着色器：
#version 410 core
uniform mat4 matrix;
out vec3 TexCoords;
layout(location = 0) in vec4 position;
layout(location = 1) in vec3 textureIn;
void main() {
TexCoords = textureIn;
gl_Position = matrix * position;
}
片段着色器：
#version 410 core
varying vec3 TexCoords;
uniform samplerCube mytexture;
void main() {
gl_FragColor = texture(mytexture, TexCoords);
}
我用来渲染的代码：
void Player::SetupScene() {
this->m_sceneVertexCount = 36;
float skyboxVertices[] = {
// positions
// Back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
float skyboxTextures[] = {
// positions
// Back
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
// Bottom
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f
};
glGenVertexArrays(1, &m_SceneVAO);
glBindVertexArray(m_SceneVAO);
glGenBuffers(1, &m_sceneVertBuffer);
glBindBuffer(GL_ARRAY_BUFFER, m_sceneVertBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxVertices), &skyboxVertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glGenBuffers(1, &m_sceneTexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, m_sceneTexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(skyboxTextures), &skyboxTextures, GL_STATIC_DRAW);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glBindVertexArray(0);
}
void Player::SetupTexture(unsigned char *textureData) {
int width = frameWidth / 3;
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
glBindTexture(GL_TEXTURE_CUBE_MAP, m_sceneTextureID);
// Render left face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render front face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render right face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render bottom face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Rotate the back face 90 degrees counter clockwise
uint8_t *start = textureData + rowLength * height * 3 + width * 3;
for (int j = 0; j < height; j++) {
for (int i = 0; i < width; i++) {
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 0] = *(start + i * 3 + 0);
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 1] = *(start + i * 3 + 1);
m_pRightFaceBuffer[((width - 1 - i) * width + j) * 3 + 2] = *(start + i * 3 + 2);
}
start += rowLength * 3;
}
glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pRightFaceBuffer);
// Rotate the bottom face 180 degrees counter clockwise
start = textureData + rowLength * height * 3 + width * 2 * 3;
for (int j = 0; j < height; j++) {
for (int i = 0; i < width; i++) {
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 0] = *(start + (i) * 3);
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 1] = *(start + (i) * 3 + 1);
m_pUpFaceBuffer[((height - 1 - j)*width + (width - i)) * 3 + 2] = *(start + (i) * 3 + 2);
}
start += rowLength * 3;
}
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pUpFaceBuffer);
}
我用来构建立方体贴图的坐标：
您可以通过glTexImage2D直接指定立方体贴图的边：
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
// Render left face
[...]
// Render front face
[...]
// Render right face
[...]
// Render bottom face
[...]
// Render back face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render top face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width*2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
但是您必须更改右侧和顶部的纹理坐标。请注意，您弄乱了立方体贴图边到立方体边的映射，但无论如何它都有效：
float skyboxTextures[] = {
// positions
// Back
// [...]
// Left
// [...]
// Right
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
// Front
// [...]
// Top
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
// Bottom
// [...]
};
查看结果：
由于侧面的映射似乎很乱，我更愿意像这样加载侧面：
glPixelStorei(GL_UNPACK_ROW_LENGTH, frameWidth);
// Render back face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render left face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render right face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width * 2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render front face
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render top face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, width*2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
// Render bottom face
glPixelStorei(GL_UNPACK_SKIP_ROWS, width);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, GL_RGB, width, width, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData);
并使用以下纹理坐标：
float skyboxTextures[] = {
// positions
// Back
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
// Left
-1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Right
1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
// Front
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 1.0f,
// Top
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
// Bottom
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f
};
但请注意，y 轴和 z 轴仍然互换。我假设这是因为场景中的世界 space 向上向量是 (0, 1, 0).