Question

我无法在我的应用程序中使用阴影贴图。我试着渲染一辆四轮摩托车并在它下面的地板上观察它的阴影。这是我的一些代码。纹理创建：

    // Create a depth texture
    glGenTextures(1, &depth_texture);
    glBindTexture(GL_TEXTURE_2D, depth_texture);
    // Allocate storage for the texture data
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32 ,1600, 900, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
    // Set the default filtering modes
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    // Set up wrapping modes
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glBindTexture(GL_TEXTURE_2D, 0);
    // Create FBO to render depth into
    glGenFramebuffers(1, &depth_fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, depth_fbo);
    // Attach the depth texture to it
    glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
    depth_texture, 0);
    // Disable color rendering as there are no color attachments
    glDrawBuffer(GL_NONE);
    //check fbo status
    GLenum result = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if(result != GL_FRAMEBUFFER_COMPLETE)
        throw std::runtime_error("shadow mapping framebuffer error");
    //bind default framebuffer
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

渲染到深度纹理：

progShadow.Use();
glBindFramebuffer(GL_FRAMEBUFFER, depth_fbo);

glClear(GL_DEPTH_BUFFER_BIT);

glm::mat4 shadowProjection = glm::frustum(-1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 100.0f);
glm::mat4 shadowView = glm::lookAt(light.position, glm::vec3(0,0,0), glm::vec3(0,1,0));
glm::mat4 shadowModel(1);
if(g_rotate)
    shadowModel = glm::rotate((float)clock() / (float)CLOCKS_PER_SEC, glm::vec3(0,1,0));
glm::mat4 shadowMVP = shadowProjection * shadowView * shadowModel;
progShadow.SetUniform("MVPMatrix", shadowMVP);
quadBike.Draw();

我也使用＆＃34;测试＆＃34;渲染程序，渲染我的深度纹理。这是它的样子。

所以我想我到现在为止都很好。现在我正常渲染场景。

glBindTexture(GL_TEXTURE_2D, depth_texture);
prog.Use();//main program
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glm::mat4 shadowBias = glm::mat4(0.5, 0.0, 0.0, 0.0,
                                 0.0, 0.5, 0.0, 0.0,
                                 0.0, 0.0, 0.5, 0.0,
                                 0.5, 0.5, 0.5, 1.0);
glm::mat4 ShadowBiasMVP = shadowBias * shadowMVP;
prog.SetUniform("ShadowBiasMVP", ShadowBiasMVP);

//draw quadBike and floor
...

我的顶点着色器的相关部分：

#version 430

...

out vec4 shadowCoord;

void main()
{
    gl_Position = ProjectionMatrix * CameraMatrix * ModelMatrix * vec4(vertex, 1.0);
    shadowCoord = ShadowBiasMVP * vec4(vertex, 1.0);
    ...
}

我的片段着色器的相关部分：

#version 430

...

uniform sampler2D shadowMap;
in vec4 shadowCoord;

void main()
{
    ...

    float visibility = 1.0;
    if ( texture(shadowMap, shadowCoord.xy).z <  shadowCoord.z)
        visibility = 0.0;

    ...
}

现在的问题是我得到一个完全黑暗的场景，好像它全都被阴影覆盖了。只有当灯光非常接近四轮摩托车时，它才能正常运行。（深度纹理在右侧可见，因为它使用不同的程序渲染。我用它进行测试） scene

我做错了什么？

Answer 1

您应该在第一个组件处读取灰度深度纹理。

texture(shadowMap, shadowCoord.xy).r或

texture(shadowMap, shadowCoord.xy).x
插值后，阴影坐标应该被去均匀化（除以w）。

- ＆GT;在片段着色器中：shadowPos = shadowPos/shadowPos.w;
如果没有使用像多边形偏移这样的其他技术，则需要从阴影深度值中减去偏差以防止自阴影。

以下是计算片段着色器中阴影的示例函数。注意：它是延迟渲染器的一部分，这就是在片段着色器中完成矩阵乘法的原因。

float calculateShadow(vec3 position){
    vec4 shadowPos = depthBiasMV * vec4(position,1);
    shadowPos = shadowPos/shadowPos.w;


     float bias =  0.0012;
     float visibility = 1.0f;
     if ((shadowPos.x < 0 || shadowPos.x > 1 || shadowPos.y < 0 || shadowPos.y > 1 || shadowPos.z < 0 || shadowPos.z > 1)){
       visibility = 1.0f;
     }else{
        float shadowDepth = texture(depthTex, shadowPos.xy).r;
        if(shadowDepth<shadowPos.z-bias)
            visibility = 0.0f;
     }
     return visibility;

}

OpenGL中的阴影贴图

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