级联阴影贴图闪闪发光

Question

我目前正在尝试了解级联阴影贴图是如何工作的，因此我一直试图让一张阴影贴图适合视锥体，而不会闪烁。我使用1到10000的近/远平面进行相机投影，这是我计算光的正交矩阵的方式：

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);

使用最长的对角线来偏移平截头体似乎是有效的，因为当看周围时阴影贴图似乎没有缩小/缩放，但是使用https://msdn.microsoft.com/en-us/library/windows/desktop/ee416324(v=vs.85).aspx描述的纹素大小增量没有任何影响。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上的分辨率很低，但是我希望在继续将截锥体分开之前得到一个适合视锥体的稳定阴影。很难从图像中分辨出来，但微软提出的解决方案并没有减少闪烁的效果：

Answer 1

结束使用此解决方案：

//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;

我在http://www.gamedev.net/topic/650743-improving-cascade-shadow/找到了我基本上切换到使用边界球，然后构建如该示例中的舍入矩阵。像魅力一样工作