级联阴影贴图波光

Question

我目前正在学习如何级联阴影贴图的工作，所以我一直在试图让一个阴影贴图以适应视锥没有闪闪发光。我使用的1近/远平面到10000我的相机投影，这是我计算的光正交矩阵方式：

GLfloat far = -INFINITY; 
GLfloat near = INFINITY; 

//Multiply all the world space frustum corners with the view matrix of the light 
Frustum cameraFrustum = CameraMan.getActiveCamera()->mFrustum; 
lightViewMatrix = glm::lookAt((cameraFrustum.frustumCenter - glm::vec3(-0.447213620f, -0.89442790f, 0.0f)), cameraFrustum.frustumCenter, glm::vec3(0.0f, 0.0f, 1.0f)); 

glm::vec3 arr[8]; 
for (unsigned int i = 0; i < 8; ++i) 
    arr[i] = glm::vec3(lightViewMatrix * glm::vec4(cameraFrustum.frustumCorners[i], 1.0f)); 

glm::vec3 minO = glm::vec3(INFINITY, INFINITY, INFINITY); 
glm::vec3 maxO = glm::vec3(-INFINITY, -INFINITY, -INFINITY); 

for (auto& vec : arr) 
{ 
    minO = glm::min(minO, vec); 
    maxO = glm::max(maxO, vec); 
} 

far = maxO.z; 
near = minO.z; 

//Get the longest diagonal of the frustum, this along with texel sized increments is used to keep the shadows from shimmering 
//far top right - near bottom left 
glm::vec3 longestDiagonal = cameraFrustum.frustumCorners[0] - cameraFrustum.frustumCorners[6]; 
GLfloat lengthOfDiagonal = glm::length(longestDiagonal); 
longestDiagonal = glm::vec3(lengthOfDiagonal); 

glm::vec3 borderOffset = (longestDiagonal - (maxO - minO)) * glm::vec3(0.5f, 0.5f, 0.5f); 

borderOffset *= glm::vec3(1.0f, 1.0f, 0.0f); 

maxO += borderOffset; 
minO -= borderOffset; 

GLfloat worldUnitsPerTexel = lengthOfDiagonal/1024.0f; 
glm::vec3 vWorldUnitsPerTexel = glm::vec3(worldUnitsPerTexel, worldUnitsPerTexel, 0.0f); 
minO /= vWorldUnitsPerTexel; 
minO = glm::floor(minO); 
minO *= vWorldUnitsPerTexel; 

maxO /= vWorldUnitsPerTexel; 
maxO = glm::floor(maxO); 
maxO *= vWorldUnitsPerTexel; 

lightOrthoMatrix = glm::ortho(minO.x, maxO.x, minO.y, maxO.y, near, far); 

使用的最长对角线来抵消视锥似乎被工作作为阴影贴图似乎并没有缩小/缩放四处寻找时，却使用https://msdn.microsoft.com/en-us/library/windows/desktop/ee416324(v=vs.85).aspx描述纹理像素大小的增量已经没有任何影响。我正在使用一个非常大的场景进行测试，这导致我的阴影贴图分辨率较低，但是我希望能够在将视锥分割开来之前获得适合视图平截头体的稳定阴影。很难从图像中说，但不是由微软提出的解决方案降低了波光粼粼的效果：

Answer 1

结束了使用此解决方案：

//Calculate the viewMatrix from the frustum center and light direction 
Frustum cameraFrustum = CameraMan.getActiveCamera()->mFrustum; 
glm::vec3 lightDirection = glm::normalize(glm::vec3(-0.447213620f, -0.89442790f, 0.0f)); 
lightViewMatrix = glm::lookAt((cameraFrustum.frustumCenter - lightDirection), cameraFrustum.frustumCenter, glm::vec3(0.0f, 1.0f, 0.0f)); 

//Get the longest radius in world space 
GLfloat radius = glm::length(cameraFrustum.frustumCenter - cameraFrustum.frustumCorners[6]); 
for (unsigned int i = 0; i < 8; ++i) 
{ 
    GLfloat distance = glm::length(cameraFrustum.frustumCorners[i] - cameraFrustum.frustumCenter); 
    radius = glm::max(radius, distance); 

} 
radius = std::ceil(radius); 

//Create the AABB from the radius 
glm::vec3 maxOrtho = cameraFrustum.frustumCenter + glm::vec3(radius); 
glm::vec3 minOrtho = cameraFrustum.frustumCenter - glm::vec3(radius); 

//Get the AABB in light view space 
maxOrtho = glm::vec3(lightViewMatrix*glm::vec4(maxOrtho, 1.0f)); 
minOrtho = glm::vec3(lightViewMatrix*glm::vec4(minOrtho, 1.0f)); 

//Just checking when debugging to make sure the AABB is the same size 
GLfloat lengthofTemp = glm::length(maxOrtho - minOrtho); 

//Store the far and near planes 
far = maxOrtho.z; 
near = minOrtho.z; 

lightOrthoMatrix = glm::ortho(minOrtho.x, maxOrtho.x, minOrtho.y, maxOrtho.y, near, far); 

//For more accurate near and far planes, clip the scenes AABB with the orthographic frustum 
//calculateNearAndFar(); 

// Create the rounding matrix, by projecting the world-space origin and determining 
// the fractional offset in texel space 
glm::mat4 shadowMatrix = lightOrthoMatrix * lightViewMatrix; 
glm::vec4 shadowOrigin = glm::vec4(0.0f, 0.0f, 0.0f, 1.0f); 
shadowOrigin = shadowMatrix * shadowOrigin; 
GLfloat storedW = shadowOrigin.w; 
shadowOrigin = shadowOrigin * 4096.0f/2.0f; 

glm::vec4 roundedOrigin = glm::round(shadowOrigin); 
glm::vec4 roundOffset = roundedOrigin - shadowOrigin; 
roundOffset = roundOffset * 2.0f/4096.0f; 
roundOffset.z = 0.0f; 
roundOffset.w = 0.0f; 

glm::mat4 shadowProj = lightOrthoMatrix; 
shadowProj[3] += roundOffset; 
lightOrthoMatrix = shadowProj; 

，我发现了在http://www.gamedev.net/topic/650743-improving-cascade-shadow/我基本上切换到使用边界球代替，然后构造如该示例中的舍入矩阵。工程就像一个魅力