OpenGL阴影映射几乎可以工作

Question

我正在尝试按照教程为我的类似 Minecraft 的克隆添加实时阴影映射：here

首先会发生什么：

据我所知，阴影贴图渲染正确吗？问题似乎出在最后一遍。

我创建深度纹理：

glGenFramebuffers(1, &m_frameBufferId);
glBindFramebuffer(GL_FRAMEBUFFER, m_frameBufferId);
glGenTextures(1, &m_depthTexture);
glBindTexture(GL_TEXTURE_2D, m_depthTexture);
glTexImage2D(GL_TEXTURE_2D, 0,GL_DEPTH_COMPONENT16, 1024, 1024, 0,GL_DEPTH_COMPONENT, GL_FLOAT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);

glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, m_depthTexture, 0);
glDrawBuffer(GL_NONE);

注意：我还尝试在着色器中使用带有 sampler2DShadow 的 GL_COMPARE_R_TO_TEXTURE。同样的结果。

然后运行两遍：

// ====================    Shadow    =====================
glBindFramebuffer(GL_FRAMEBUFFER, m_frameBufferId);
glViewport(0, 0, 1024, 1024);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

ShadowShader->Bind();
VCSceneGraph::Instance->RenderGraph();


// ====================    Final    =======================
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glViewport(0, 0, 1280, 800);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

VoxelShader->Bind();
VCSceneGraph::Instance->RenderGraph();

阴影着色器代码：

// ====================    Vert    =====================
#version 330 core\n

in vec4 vertexPosition_modelspace;
uniform mat4 depthMVP;

void main()
{
    gl_Position =  depthMVP * vertexPosition_modelspace;
}

// ====================    Frag    =====================
#version 330 core\n

out float fragmentdepth;

void main()
{
    fragmentdepth = gl_FragCoord.z;
}

Final-Pass（体素着色器）代码：

// ====================    Vert    =====================
#version 330 core\n

in vec3 position;
in int normal;
in vec4 color;

out vec4 colorVarying;
out vec4 ShadowCoord;

uniform mat4 modelViewProjectionMatrix;
uniform mat4 DepthBiasMVP;

void main()
{
    gl_Position =  modelViewProjectionMatrix * vec4(position, 1);
    ShadowCoord = DepthBiasMVP * vec4(position, 1);
    colorVarying = color;
}

// ====================    Frag    =====================
#version 330 core\n

in vec4 colorVarying;
in vec4 ShadowCoord;

out vec4 color;

uniform sampler2D  shadowMap;

void main()
{
    float visibility = 1.0;

    if ( texture(shadowMap, ShadowCoord.xy).z  <  ShadowCoord.z)
    {
        visibility = 0.5;
    }

    color.xyz = colorVarying.xyz * visibility;
    color.w = colorVarying.w;
}

我怀疑我的问题在于更新制服以进行最后一关的代码：

// Re-create the exact same MVP matrix that was used for the shadow pass
glm::mat4 depthProjectionMatrix = glm::ortho<float>( -30, 30, -30, 30, -100, 100);
glm::mat4 depthViewMatrix = glm::lookAt(glm::vec3(0.5f, 2, 2), glm::vec3(0,0,0), glm::vec3(0,1,0));
depthViewMatrix = glm::translate(depthViewMatrix, -15.0f, 30.0f, 0.0f);
glm::mat4 depthMVP = depthProjectionMatrix * depthViewMatrix;// * modelMatrix;

// Multiply it be the bias matrix
glm::mat4 biasMatrix
(
    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 depthBiasMVP = biasMatrix * depthMVP;

// Create Camera's MVP
VCCamera* currentCamera = VCSceneGraph::Instance->CurrentRenderingCamera;
glm::mat4 ProjectionMatrix = currentCamera->ProjectionMatrix;
glm::mat4 ViewMatrix = currentCamera->ViewMatrix;
glm::mat4 MVP = ProjectionMatrix * ViewMatrix;// * modelMatrix;

// Update uniforms
glUniformMatrix4fv(m_unifMVP, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(m_unifDepthMVP, 1, GL_FALSE, &depthBiasMVP[0][0]);

编辑：

我通过使阴影纹理与窗口具有相同的分辨率解决了这个问题。但是，我无法解释为什么会解决它。如果其他人想破解它，我会接受你的回答。预期的输出是这样的：

我还应该注意到完整的源代码可以在：GitHub.

Answer 1

我比较了你和我的影子，我建议你使用sampler2DShadow 而不是sampler2D。此采样器仅用于阴影，并且有一些阴影投影功能（shadow2DProj 等）。你可以这样使用它。

in vec4 colorVarying;
varying vec4 ShadowCoord;

out vec4 color;

uniform sampler2DShadow shadowMap;

float offset_lookup(sampler2DShadow map, vec4 loc, vec2 offset) {
    //Texture size (1024 x 1024)
    vec2 texmapscale = vec2(1.0/1024.0, 1.0/1024.0);
    //Set bias as you need (it corrects shadow acne)
    float bias = 0.001;
    vec4 result = shadow2DProj(map, vec4(loc.xy + offset * texmapscale * loc.w, loc.z, loc.w));
    if (loc.z > result.z + bias) {
        return 0.5;
    } else {
        return 1.0;
    }
}

void main() {
    float shadowFactor;
    shadowFactor = offset_lookup(shadowMap, ShadowCoord, vec2(0, 0));
    color = colorVarying * shadowFactor;
}

什么是最后一个参数偏移量？你可以做一些阴影模糊。 3x3 阴影模糊：

//3x3 blur
    for (y = -1.5; y <= 1.5; y += 1.0)
        for (x = -1.5; x <= 1.5; x += 1.0)
            sum += offset_lookup(shadowMap, ShadowCoord, vec2(x, y));
    //I am no sure why 16 (insted of 9) but I use this and it works :D
    float shadeFactor = sum / 16.0;

试试吧，也许结果会如你所愿。

PS：对不起我的英语。