我已经从灯光的角度成功地将场景渲染到了深度立方体贴图上，但是我不太了解如何将其实际投影到场景上。
以下是当前情况的简短片段：http://youtu.be/54WXDWxqmXw
我在这里找到了一个实现示例：
http://www.opengl.org/discussion_boards/showthread.php/174093-GLSL-cube-shadows-projecting?p=1219162&viewfull=1#post1219162
这似乎很容易理解，所以我认为这是一个很好的起点，但是我在使用矩阵时遇到了一些困难（如上面的视频所示）。
我的顶点着色器：
#version 330 core
layout(std140) uniform ViewProjection
{
mat4 V;
mat4 P;
};
layout(location = 0) in vec3 vertexPosition;
layout(location = 1) in vec2 vertexUV;
out vec2 UV;
out vec4 posCs;
uniform mat4 M;
uniform mat4 lightView;
void main()
{
mat4 MVP = P *V *M;
gl_Position = MVP *vec4(vertexPosition,1);
UV = vertexUV;
posCs = V *M *vec4(vertexPosition,1);
}
片段着色器：
#version 330 core
in vec2 UV;
in vec4 posCs;
out vec4 color;
// Diffuse texture
uniform sampler2D renderTexture;
uniform samplerCubeShadow shadowCubeMap;
uniform mat4 lightView;
uniform mat4 lightProjection;
uniform mat4 camViewInv;
void main()
{
color = texture2D(renderTexture,UV).rgba;
mat4 lView = mat4(1); // The light is currently at the world origin, so we'll skip the transformation for now (The less potential error sources the better)
vec4 posLs = lView *camViewInv *posCs;
vec4 posAbs = abs(posLs);
float fs_z = -max(posAbs.x,max(posAbs.y,posAbs.z));
vec4 clip = lightProjection *vec4(0.0,0.0,fs_z,1.0);
float depth = (clip.z /clip.w) *0.5 +0.5;
vec4 r = shadowCube(shadowCubeMap,vec4(posLs.xyz,depth));
color *= r;
}
（我只发布了相关部分）
lightProjection与我用于将场景渲染到立方体贴图中的投影矩阵相同。
我对“ camViewInv”并不完全确定，从上面链接的示例中我得出以下结论：
glm::mat4 camViewInv(
camView[0][0],camView[1][0],camView[2][0],0.0f,
camView[0][1],camView[1][1],camView[2][1],0.0f,
camView[0][2],camView[1][2],camView[2][2],0.0f,
camPos[0],camPos[1],camPos[2],1.0f
);
camView是相机的视图矩阵，并且camPos相机的世界空间位置。
我认为，其他所有内容都应不言自明。
我看不到着色器有任何问题，但我可以肯定，场景已正确渲染到立方体贴图（如上面的视频所示）。也许有人比我更精通此事。
//更新：
有关阴影立方体贴图的创建/用法的一些其他信息：
创建立方体贴图纹理：
unsigned int frameBuffer;
glGenFramebuffers(1,&frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER,frameBuffer);
unsigned int texture;
glGenTextures(1,&texture);
glBindTexture(GL_TEXTURE_CUBE_MAP,texture);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_COMPARE_FUNC,GL_LEQUAL);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_WRAP_R,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_WRAP_T,GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_COMPARE_MODE,GL_COMPARE_R_TO_TEXTURE);
for(int i=0;i<6;i++)
{
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X +i,0,GL_DEPTH_COMPONENT,size,size,0,GL_DEPTH_COMPONENT,GL_FLOAT,0);
glFramebufferTexture2D(GL_FRAMEBUFFER,GL_DEPTH_ATTACHMENT,GL_TEXTURE_CUBE_MAP_POSITIVE_X +i,texture,0);
glDrawBuffer(GL_NONE);
}
光的矩阵：
glm::perspective<float>(90.f,1.f,2.f,m_distance); // Projection Matrix
// View Matrices
glm::vec3 pos = GetPosition(); // Light worldspace position
glm::lookAt(pos,pos +glm::vec3(1,0,0),glm::vec3(0,1,0));
glm::lookAt(pos,pos +glm::vec3(-1,0,0),glm::vec3(0,1,0));
glm::lookAt(pos,pos +glm::vec3(0,1,0),glm::vec3(0,0,-1))
glm::lookAt(pos,pos +glm::vec3(0,-1,0),glm::vec3(0,0,1))
glm::lookAt(pos,pos +glm::vec3(0,0,1),glm::vec3(0,1,0))
glm::lookAt(pos,pos +glm::vec3(0,0,-1),glm::vec3(0,1,0))
顶点着色器：
#version 330 core
layout(location = 0) in vec4 vertexPosition;
uniform mat4 shadowMVP;
void main()
{
gl_Position = shadowMVP *vertexPosition;
}
片段着色器：
#version 330 core
layout(location = 0) out float fragmentDepth;
void main()
{
fragmentdepth = gl_FragCoord.z;
}
最佳答案
我建议在世界空间中执行此操作，通常在世界空间中定义灯光位置，如果保持这种方式，它将减少工作量。我删除了一堆在世界空间中不需要的制服。
以vtx计算照明方向和深度。着色器：
#version 330 core
layout(std140) uniform ViewProjection
{
mat4 V;
mat4 P;
};
layout(location = 0) in vec4 vertexPosition; // W is automatically assigned 1, if missing.
layout(location = 1) in vec2 vertexUV;
out vec2 UV;
out vec4 lightDirDepth; // Direction = xyz, Depth = w
uniform mat4 M;
uniform vec3 lightPos; // World Space Light Pos
uniform vec2 shadowZRange; // Near / Far clip plane distances for shadow's camera
float vecToDepth (vec3 Vec)
{
vec3 AbsVec = abs (Vec);
float LocalZcomp = max (AbsVec.x, max (AbsVec.y, AbsVec.z));
const float n = shadowZRange [0]; // Near plane when the shadow map was built
const float f = shadowZRange [1]; // Far plane when the shadow map was built
float NormZComp = (f+n) / (f-n) - (2.0*f*n)/(f-n)/LocalZcomp;
return (NormZComp + 1.0) * 0.5;
}
void main()
{
mat4 MVP = P *V *M;
gl_Position = MVP *vertexPosition;
UV = vertexUV;
vec3 lightDir = lightPos - (M *vertexPosition).xyz;
float lightDepth = vecToDepth (lightDir);
lightDirDepth = vec4 (lightDir, lightDepth);
}
修改后的片段着色器（使用光照方向采样立方体贴图，并针对深度进行测试）：
#version 330 core
in vec2 UV;
in vec4 lightDirDepth; // Direction = xyz, Depth = w
out vec4 color;
// Diffuse texture
uniform sampler2D renderTexture;
uniform samplerCubeShadow shadowCubeMap;
void main()
{
const float bias = 0.0001; // Prevent shadow acne
color = texture (renderTexture,UV).rgba;
float r = texture (shadowCubeMap, vec4 (lightDirDepth.xyz, lightDirDepth.w + bias));
color *= r;
}
我增加了两套新制服：
lightPos-灯光的世界空间位置shadowZRange-构建阴影立方体贴图时打包在vec2中的近平面和远平面的值让我知道您是否需要我解释什么，或者这没有产生有意义的结果。