OpenGLShader实例分析（2）绘制心脏跳动效果-创新互联

本文将介绍怎么用Shader来绘制一个跳动的心脏。这里会涉及到一些数学知识。先看效果图：

源代码如下：

// Created by inigo quilez - iq/2013
// License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
// changed by stalendp@gmail.com
Shader "shadertoy/Heart" { // see https://www.shadertoy.com/view/XsfGRn
 CGINCLUDE 
 
 #include "UnityCG.cginc"  
 #pragma target 3.0 
 struct vertOut { 
  float4 pos:SV_POSITION; 
  float4 srcPos; 
 }; 
 
 vertOut vert(appdata_base v) { 
  vertOut o; 
  o.pos = mul (UNITY_MATRIX_MVP, v.vertex); 
  return o; 
 } 
 
 fixed4 frag(float4 sp:WPOS) : COLOR0 { 
 float2 p = (2.0*sp.xy - _ScreenParams.xy) / min(_ScreenParams.y, _ScreenParams.x);
 p.y -= 0.25;
 
 //background color
 float3 bcol = float3(1.0,0.8,0.7-0.07*p.y) * (1.0 - 0.25*length(p));
 
 // animate
 float tt = fmod(_Time.y, 1.5)/1.5;
 float ss = pow(tt,.2) * 0.5 + 0.5;
 ss -= ss*0.2*sin(tt*6.2831*3.0)*exp(-tt*4.0);
 p *= float2(0.5, 1.5) + ss * float2(0.5, -0.5);
 
 // shape
 float a = atan2(p.x,p.y)/3.141593;
 float r = length(p);
 float h = abs(a);
 float d = (13.0*h - 22.0*h*h + 10.0*h*h*h)/(6.0-5.0*h);
 
 // color
 float s = 1.0-0.5*clamp(r/d,0.0,1.0);
 s = 0.75 + 0.75*p.x;
 s *= 1.0-0.25*r;
 s = 0.5 + 0.6*s;
 s *= 0.5+0.5*pow( 1.0-clamp(r/d, 0.0, 1.0 ), 0.1 );
 float3 hcol = float3(1.0,0.5*r,0.3)*s;
 
 float3 col = lerp( bcol, hcol, smoothstep( -0.01, 0.01, d-r) );
 
 return float4(col,1.0);
 } 
 
 ENDCG 
 
 SubShader { 
 Pass { 
  CGPROGRAM 
 
  #pragma vertex vert 
  #pragma fragment frag 
  #pragma fragmentoption ARB_precision_hint_fastest 
 
  ENDCG 
 } 
 
 } 
 FallBack Off 
}