阴影映射中具有汇总面积表的数值稳定性
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我在SAVSM设置中失去精度问题。
当您看到光线四处移动时，效果非常惊人；有很多噪音，碎片一直在黑白相间。通过使用最小方差可以略微减小这种影响（因此忽略了低于某个阈值的任何东西），但是如果不正确的衰减，我们会得到更差的效果（请参阅我的其他文章）。
我使用GLSL 1.2是因为我在Mac上，因此我无法访问modf函数，无法按照GPU Gems 3第8章中的描述在两个通道之间分配精度。
我将GL_RGBA32F_ARB纹理与Framebuffer对象一起使用，并且对两个纹理进行ping操作以生成一个总面积表，并将其与VSM算法一起使用。
Moments / Depth Shader创建表格的基础
varying vec4 v_position;
varying float tDepth;
float g_DistributeFactor = 1024.0;
void main()
{
// Is this linear depth? I would say yes but one can\'t be utterly sure.
// Could try a divide by the far plane?
float depth = v_position.z / v_position.w ;
depth = depth * 0.5 + 0.5; //Don\'t forget to move away from unit cube ([-1,1]) to [0,1] coordinate system
vec2 moments = vec2(depth, depth * depth);
// Adjusting moments (this is sort of bias per pixel) using derivative
float dx = dFdx(depth);
float dy = dFdy(depth);
moments.y += 0.25 * (dx*dx+dy*dy);
// Subtract 0.5 off now so we can get this into our summed area table calc
//moments -= 0.5;
// Split the moments into rg and ba for EVEN MORE PRECISION
// float FactorInv = 1.0 / g_DistributeFactor;
// gl_FragColor = vec4(floor(moments.x) * FactorInv, fract(moments.x ) * g_DistributeFactor,
// floor(moments.y) * FactorInv, fract(moments.y) * g_DistributeFactor);
gl_FragColor = vec4(moments,0.0,0.0);
}
varying vec4 v_position;
varying float tDepth;
float g_DistributeFactor = 1024.0;
void main()
{
// Is this linear depth? I would say yes but one can\'t be utterly sure.
// Could try a divide by the far plane?
float depth = v_position.z / v_position.w ;
depth = depth * 0.5 + 0.5; //Don\'t forget to move away from unit cube ([-1,1]) to [0,1] coordinate system
vec2 moments = vec2(depth, depth * depth);
// Adjusting moments (this is sort of bias per pixel) using derivative
float dx = dFdx(depth);
float dy = dFdy(depth);
moments.y += 0.25 * (dx*dx+dy*dy);
// Subtract 0.5 off now so we can get this into our summed area table calc
//moments -= 0.5;
// Split the moments into rg and ba for EVEN MORE PRECISION
// float FactorInv = 1.0 / g_DistributeFactor;
// gl_FragColor = vec4(floor(moments.x) * FactorInv, fract(moments.x ) * g_DistributeFactor,
// floor(moments.y) * FactorInv, fract(moments.y) * g_DistributeFactor);
gl_FragColor = vec4(moments,0.0,0.0);
}
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