java - 用于流体模拟的双边滤波器

Question

所以我有一个流体模拟，我正在尝试应用双边过滤器，以便在保留边缘的同时模糊表面。我的方法基于此演示文稿(特别是幻灯片 26)http://developer.download.nvidia.com/presentations/2010/gdc/Direct3D_Effects.pdf

我遇到的问题是根本没有保留我的边缘。即使我渲染出单个粒子，它也会被模糊，正如您在下图中看到的那样，模糊是不正确的。

此外，如 pdf 中所述，虽然分离双边过滤器通常是 Not Acceptable ，但在流体的情况下这样做是合理的，因为只有轻微的伪影。这就是下面两个 pass 的原因，但这不应该导致边缘模糊。

模糊着色器:

#version 400

in vec2 coord;

uniform sampler2D depthMap;
uniform vec2 screenSize;
uniform mat4 projection;
uniform vec2 blurDir;

const float filterRadius = 10;
const float blurScale = .1;
const float blurDepthFalloff = 1000;

 void main() {
     float depth = texture(depthMap, coord).x;

     float sum = 0.0f;
     float wsum = 0.0f;

     for (float x = -filterRadius; x <= filterRadius; x += 1.0f) {
        float s = texture(depthMap, coord + x*blurDir).x;

        float r = x * blurScale;
        float w = exp(-r*r);

        float r2 = (s - depth) * blurDepthFalloff;
        float g = exp(-r2*r2);

        sum += s * w * g;
        wsum += w * g;
    }

    if (wsum > 0.0f) {
        sum /= wsum;
    }

    gl_FragDepth = sum;
}

绘图代码:

//--------------------Particle Blur-------------------------
        {
            glUseProgram(blurShader.program);

            //Vertical blur
            glBindFramebuffer(GL_FRAMEBUFFER, blurShader.fboV);
            glDrawBuffer(GL_NONE);
            glReadBuffer(GL_NONE);

            glClear(GL_DEPTH_BUFFER_BIT);

            blurShader.blurDepthVAO();

            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D, depthShader.tex);
            glUniform1i(blurShader.depthMap, 0);

            RenderUtility.setVector2(blurShader, screenSize, "screenSize");
            RenderUtility.setMatrix(blurShader, projection, "projection");
            RenderUtility.setVector2(blurShader, new Vector2(0.0f, 1.0f / screenSize.y), "blurDir");

            glEnable(GL_DEPTH_TEST);

            glBindVertexArray(blurShader.vao);

            glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

            //Horizontal Blur
            glBindFramebuffer(GL_FRAMEBUFFER, blurShader.fboH);
            glDrawBuffer(GL_NONE);
            glReadBuffer(GL_NONE);

            glClear(GL_DEPTH_BUFFER_BIT);

            glActiveTexture(GL_TEXTURE0);
            glBindTexture(GL_TEXTURE_2D, blurShader.texV);
            glUniform1i(blurShader.depthMap, 0);

            RenderUtility.setVector2(blurShader, screenSize, "screenSize");
            RenderUtility.setMatrix(blurShader, projection, "projection");
            RenderUtility.setVector2(blurShader, new Vector2(1.0f / screenSize.x, 0.0f), "blurDir");

            glEnable(GL_DEPTH_TEST);

            glBindVertexArray(blurShader.vao);

            glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
        }

当前状态图:

Answer 1

终于明白了。缺少的部分是深度大于 .9999(或其他最大深度数)的像素需要被丢弃，这样您就不会试图模糊不属于模拟的像素。回想起来很明显，但我花了很长时间才意识到。

因此正确的着色器如下所示:

uniform sampler2D depthMap;
uniform vec2 screenSize;
uniform mat4 projection;
uniform vec2 blurDir;

const float filterRadius = 10;
const float blurScale = .1;
const float blurDepthFalloff = 1000;

void main() {
    float depth = texture(depthMap, coord).x;
    if (depth == 1.0f) {
       discard;
    }

    float sum = 0.0f;
    float wsum = 0.0f;

    for (float x = -filterRadius; x <= filterRadius; x += 1.0f) {
        float s = texture(depthMap, coord + x*blurDir).x;

        float r = x * blurScale;
        float w = exp(-r*r);

        float r2 = (s - depth) * blurDepthFalloff;
        float g = exp(-r2*r2);

        sum += s * w * g;
        wsum += w * g;
    }

    if (wsum > 0.0f) {
        sum /= wsum;
    }

    gl_FragDepth = sum;
}