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soft shadow in ParallaxOcclusionMapping


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#1 Jeason   Members   -  Reputation: 96

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Posted 04 March 2012 - 03:44 AM

I get the codes in ParallaxOcclusionMapping sample in DX9.
Is there any theory or basis behind the codes, especially the number and weight ?
		  float2 vLightRayTS = vLightTS.xy * g_fHeightMapScale;
	 
	    // Compute the soft blurry shadows taking into account self-occlusion for
	    // features of the height field:
  
	    float sh0 =  tex2Dgrad( tNormalHeightMap, texSampleBase, dx, dy ).a;
	    float shA = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.88, dx, dy ).a - sh0 - 0.88 ) *  1 * g_fShadowSoftening;
	    float sh9 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.77, dx, dy ).a - sh0 - 0.77 ) *  2 * g_fShadowSoftening;
	    float sh8 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.66, dx, dy ).a - sh0 - 0.66 ) *  4 * g_fShadowSoftening;
	    float sh7 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.55, dx, dy ).a - sh0 - 0.55 ) *  6 * g_fShadowSoftening;
	    float sh6 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.44, dx, dy ).a - sh0 - 0.44 ) *  8 * g_fShadowSoftening;
	    float sh5 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.33, dx, dy ).a - sh0 - 0.33 ) * 10 * g_fShadowSoftening;
	    float sh4 = (tex2Dgrad( tNormalHeightMap, texSampleBase + vLightRayTS * 0.22, dx, dy ).a - sh0 - 0.22 ) * 12 * g_fShadowSoftening;
  
	    // Compute the actual shadow strength:
	    fOcclusionShadow = 1 - max( max( max( max( max( max( shA, sh9 ), sh8 ), sh7 ), sh6 ), sh5 ), sh4 );
	 
	    // The previous computation overbrightens the image, let's adjust for that:
	    fOcclusionShadow = fOcclusionShadow * 0.6 + 0.4;

Please help me!

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