如何正确制作阴影贴图的深度立方体贴图？

在兼容性配置文件中使用GL 3.3.

这是我创建FBO和立方体贴图纹理的代码：

glGenFramebuffers(1,&fboShadow);
    glGenTextures(1,&texShadow);
    glBindTexture(GL_TEXTURE_CUBE_MAP,texShadow);
    for (int sideId = 0; sideId < 6; sideId++) {
        // Make sure GL knows what this is going to be.
        glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + sideId,GL_DEPTH_COMPONENT,512,GL_FLOAT,NULL);
    }

    // Don't interpolate depth value sampling. Between occluder and occludee there will
    // be an instant jump in depth value,not a linear transition.
    glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_MIN_FILTER,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP,GL_TEXTURE_WRAP_T,GL_TEXTURE_WRAP_R,GL_CLAMP_TO_EDGE);

    glBindTexture(GL_TEXTURE_CUBE_MAP,0);

我的完整渲染功能如下所示：

void render() {

    // --- MAKE DEPTH CUBEMAP ---

    // Set shader program for depth testing
    glUseProgram(progShadow);

    // Get the light for which we want to generate a depth cubemap
    PointLight p = pointLights.at(0);

    // Bind our framebuffer for drawing; clean it up
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER,fboShadow);
    glClear(GL_DEPTH_BUFFER_BIT);

    // Make 1:1-ratio,90-degree view frustum for a 512x512 texture.
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(90.0,1,16.0,16384.0);
    glViewport(0,512);
    glMatrixMode(GL_MODELVIEW);

    // Set modelview and projection matrix uniforms
    setShadowUniforms();

    // Need 6 renderpasses to complete each side of the cubemap
    for (int sideId = 0; sideId < 6; sideId++) {
        // Attach depth attachment of current framebuffer to level 0 of currently relevant target of texShadow cubemap texture.
        glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER,GL_DEPTH_ATTACHMENT,GL_TEXTURE_CUBE_MAP_POSITIVE_X + sideId,texShadow,0);

        // All is fine.
        GLenum status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
        if (status != GL_FRAMEBUFFER_COMPLETE) {
            std::cout << "Shadow FBO is broken with code " << status << std::endl;
        }

        // Push modelview matrix stack because we need to rotate and move camera every time
        glPushMatrix();

        // This does a switch-case with glRotatefs
        rotateCameraForSide(GL_TEXTURE_CUBE_MAP_POSITIVE_X + sideId);

        // Render from light's position.
        glTranslatef(-p.getX(),-p.getY(),-p.getZ());

        // Render all objects.
        for (ObjectList::iterator it = objectList.begin(); it != objectList.end(); it++) {
            (*it)->render();
        }

        glPopMatrix();
    }


    // --- RENDER SCENE ---

    // Bind default framebuffer
    glBindFramebuffer(GL_FRAMEBUFFER,0);

    // Setup proper projection matrix with 70 degree vertical FOV and ratio according to window frame dimensions.
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(70.0,((float)vpWidth) / ((float)vpHeight),vpWidth,vpHeight);

    glUseProgram(prog);

    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();

    applyCameraPerspective();

    // My PointLight class has both a position (world space) and renderPosition (camera space) Vec3f variable;
    // The lights' renderPositions get transformed with the modelview matrix by this.
    updateLights();

    // And here,among other things,the lights' camera space coordinates go to the shader.
    setUniforms();

    // Render all objects
    for (ObjectList::iterator it = objectList.begin(); it != objectList.end(); it++) {

        // Object texture goes to texture unit 0
        GLuint usedTexture = glTextureList.find((*it)->getTextureName())->second;
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D,usedTexture);
        glUniform1i(textureLoc,0);

        // Cubemap goes to texture unit 1
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_CUBE_MAP,texShadow);
        glUniform1i(shadowLoc,1);

        (*it)->render();
    }

    glPopMatrix();
    frameCount++;
}

用于渲染深度值的着色器程序(“progShadow”)很简单.

顶点着色器：

#version 330

in vec3 position;

uniform mat4 modelViewMatrix,projectionMatrix;

void main() {
    gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1);
}

片段着色器：

#version 330

void main() {
    // OpenGL sets the depth anyway. Nothing to do here.
}

最终渲染的着色器程序(“prog”)有一个片段着色器,看起来像这样：

#version 330

#define MAX_LIGHTS 8

in vec3 fragPosition;
in vec3 fragNormal;
in vec2 fragTexCoordinates;
out vec4 fragColor;

uniform sampler2D colorTexture;
uniform samplerCubeShadow shadowCube;

uniform uint activeLightCount;

struct Light {
    vec3 position;
    vec3 diffuse;
    float cAtt;
    float lAtt;
    float qAtt;
};

// Index 0 to (activeLightCount - 1) need to be the active lights.
uniform Light lights[MAX_LIGHTS];

void main() {
    vec3 lightColor = vec3(0,0);
    vec3 normalFragmentToLight[MAX_LIGHTS];
    float distFragmentToLight[MAX_LIGHTS];
    float distEyeToFragment = length(fragPosition);

    // Accumulate all light in "lightColor" variable
    for (uint i = uint(0); i < activeLightCount; i++) {
        normalFragmentToLight[i] = normalize(lights[i].position - fragPosition);
        distFragmentToLight[i] = distance(fragPosition,lights[i].position);
        float attenuation = (lights[i].cAtt
            + lights[i].lAtt * distFragmentToLight[i]
            + lights[i].qAtt * pow(distFragmentToLight[i],2.0));

        float dotProduct = dot(fragNormal,normalFragmentToLight[i]);
        lightColor += lights[i].diffuse * max(dotProduct,0.0) / attenuation;
    }

    // Shadow mapping only for light at index 0 for now.
    float distOccluderToLight = texture(shadowCube,vec4(normalFragmentToLight[0],1));

    // My geometries use inches as units,hence a large bias of 1
    bool isLit = (distOccluderToLight + 1) < distFragmentToLight[0];
    fragColor = texture2D(colorTexture,fragTexCoordinates) * vec4(lightColor,1.0f) * int(isLit);
}

我已经验证所有均匀位置变量都设置为适当的值(即不是-1).

值得注意的是,在链接之前我没有为“progShadow”调用glBindFragDataLocation(),因为该着色器不应该写入颜色值.

看到任何明显错误的地方？