多重采样MSAA

GLSurfaceView设置多重采样

/**
 * 抗锯齿EGLConfigChooser
 *
 * author weiss
 * email kleinminamo@gmail.com
 * created 2018/7/3.
 */
public class MSAAConfigChooser implements GLSurfaceView.EGLConfigChooser {
    @Override
    public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display) {

        int attribs[] = {
                EGL10.EGL_LEVEL, 0,
                EGL10.EGL_RENDERABLE_TYPE, 4,  // EGL_OPENGL_ES2_BIT
                EGL10.EGL_COLOR_BUFFER_TYPE, EGL10.EGL_RGB_BUFFER,
                EGL10.EGL_RED_SIZE, 8,
                EGL10.EGL_GREEN_SIZE, 8,
                EGL10.EGL_BLUE_SIZE, 8,
                EGL10.EGL_DEPTH_SIZE, 24,
                EGL10.EGL_SAMPLE_BUFFERS, 1,
                EGL10.EGL_SAMPLES, 4,  // 在这里修改MSAA的倍数，4就是4xMSAA，再往上开程序可能会崩
                EGL10.EGL_NONE
        };
        EGLConfig[] configs = new EGLConfig[1];
        int[] configCounts = new int[1];
        egl.eglChooseConfig(display, attribs, configs, 1, configCounts);

        if (configCounts[0] == 0) {
            // Failed! Error handling.
            return null;
        } else {
            return configs[0];
        }
    }
}

后处理FXAA Shader

#ifndef FXAA_REDUCE_MIN
    #define FXAA_REDUCE_MIN   (1.0/ 128.0)
#endif
#ifndef FXAA_REDUCE_MUL
    #define FXAA_REDUCE_MUL   (1.0 / 8.0)
#endif
#ifndef FXAA_SPAN_MAX
    #define FXAA_SPAN_MAX     8.0
#endif

//optimized version for mobile, where dependent
//texture reads can be a bottleneck
vec4 fxaa(sampler2D tex, vec2 fragCoord, vec2 resolution,
            vec2 v_rgbNW, vec2 v_rgbNE,
            vec2 v_rgbSW, vec2 v_rgbSE,
            vec2 v_rgbM) {
    vec4 color;
    mediump vec2 inverseVP = vec2(1.0 / resolution.x, 1.0 / resolution.y);
    vec3 rgbNW = texture2D(tex, v_rgbNW).xyz;
    vec3 rgbNE = texture2D(tex, v_rgbNE).xyz;
    vec3 rgbSW = texture2D(tex, v_rgbSW).xyz;
    vec3 rgbSE = texture2D(tex, v_rgbSE).xyz;
    vec4 texColor = texture2D(tex, v_rgbM);
    vec3 rgbM  = texColor.xyz;
    vec3 luma = vec3(0.299, 0.587, 0.114);
    float lumaNW = dot(rgbNW, luma);
    float lumaNE = dot(rgbNE, luma);
    float lumaSW = dot(rgbSW, luma);
    float lumaSE = dot(rgbSE, luma);
    float lumaM  = dot(rgbM,  luma);
    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));
    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));

    mediump vec2 dir;
    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));
    dir.y =  ((lumaNW + lumaSW) - (lumaNE + lumaSE));

    float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) *
                          (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);

    float rcpDirMin = 1.0 / (min(abs(dir.x), abs(dir.y)) + dirReduce);
    dir = min(vec2(FXAA_SPAN_MAX, FXAA_SPAN_MAX),
              max(vec2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX),
              dir * rcpDirMin)) * inverseVP;

    vec3 rgbA = 0.5 * (
        texture2D(tex, fragCoord * inverseVP + dir * (1.0 / 3.0 - 0.5)).xyz +
        texture2D(tex, fragCoord * inverseVP + dir * (2.0 / 3.0 - 0.5)).xyz);
    vec3 rgbB = rgbA * 0.5 + 0.25 * (
        texture2D(tex, fragCoord * inverseVP + dir * -0.5).xyz +
        texture2D(tex, fragCoord * inverseVP + dir * 0.5).xyz);

    float lumaB = dot(rgbB, luma);
    if ((lumaB < lumaMin) || (lumaB > lumaMax))
        color = vec4(rgbA, texColor.a);
    else
        color = vec4(rgbB, texColor.a);
    return color;
}

特别注意用了后处理FBO，多重采样会失效，离屏渲染需要对FBO进行多重采样

FBO

    const char* __glExtensions = (const char*)glGetString(GL_EXTENSIONS);
    if(strstr(__glExtensions, "GL_IMG_multisampled_render_to_texture"))
    {
        if(glFramebufferTexture2DMultisampleIMG_ == NULL)
        {
            glFramebufferTexture2DMultisampleIMG_ = (PFNGLFRAMEBUFFERTEXTURE2DMULTISAMPLEIMGPROC )eglGetProcAddress ( "glFramebufferTexture2DMultisampleIMG" );
        }
    }
    else if(strstr(__glExtensions, "GL_EXT_multisampled_render_to_texture"))
    {
        if(glFramebufferTexture2DMultisampleIMG_ == NULL)
        {
            glFramebufferTexture2DMultisampleIMG_ = (PFNGLFRAMEBUFFERTEXTURE2DMULTISAMPLEIMGPROC )eglGetProcAddress ( "glFramebufferTexture2DMultisampleEXT" );
        }
    }

            //glFramebufferTexture2DMultisampleIMG_
            if(_multiSample)
            {
                GL_ASSERT( glFramebufferTexture2DMultisampleIMG_(GL_FRAMEBUFFER, attachment, textureTarget, _renderTargets[index]->getTexture()->getHandle(), 0, 4););
            } else{
                GL_ASSERT( glFramebufferTexture2D(GL_FRAMEBUFFER, attachment, textureTarget, _renderTargets[index]->getTexture()->getHandle(), 0));
            }

RBO

    const char* __glExtensions = (const char*)glGetString(GL_EXTENSIONS);
    if(strstr(__glExtensions, "GL_IMG_multisampled_render_to_texture"))
    {
        if(glRenderbufferStorageMultisampleIMG_ == NULL)
        {
            glRenderbufferStorageMultisampleIMG_ = (PFNGLRENDERBUFFERSTORAGEMULTISAMPLEIMGPROC )eglGetProcAddress ( "glRenderbufferStorageMultisampleIMG" );
        }
    }
    else if(strstr(__glExtensions, "GL_EXT_multisampled_render_to_texture"))
    {
        if(glRenderbufferStorageMultisampleIMG_ == NULL)
        {
            glRenderbufferStorageMultisampleIMG_ = (PFNGLRENDERBUFFERSTORAGEMULTISAMPLEIMGPROC )eglGetProcAddress ( "glRenderbufferStorageMultisampleEXT" );
        }
    }

        //glRenderbufferStorageMultisampleIMG_
        glRenderbufferStorageMultisampleIMG_(GL_RENDERBUFFER, 4,
                                             GL_DEPTH24_STENCIL8, width, height); // w width, h height.