From 3fdabc260f24e651c4c963de056bbd9679b04555 Mon Sep 17 00:00:00 2001
From: amandaghassaei <amandaghassaei@gmail.com>
Date: Sun, 2 Apr 2017 22:18:56 -0400
Subject: [PATCH] compute pressure
---
index.html | 41 +++++++++++++++++++++++++++++++++--------
main.js | 43 +++++++++++++++++++++++++++++--------------
2 files changed, 62 insertions(+), 22 deletions(-)
diff --git a/index.html b/index.html
index 373a119..6220bad 100644
--- a/index.html
+++ b/index.html
@@ -29,6 +29,30 @@
}
</script>
+ <script id="divergenceShader" type="x-shader/x-fragment">
+ precision mediump float;
+
+ uniform sampler2D u_velocity;
+
+ uniform vec2 u_textureSize;
+
+ uniform float u_halfReciprocalDx;
+
+ void main() {
+
+ vec2 fragCoord = gl_FragCoord.xy;
+
+ //finite difference formulation of divergence
+
+ float n = texture2D(u_velocity, (fragCoord+vec2(0.0, 1.0))/u_textureSize).y;
+ float s = texture2D(u_velocity, (fragCoord+vec2(0.0, -1.0))/u_textureSize).y;
+ float e = texture2D(u_velocity, (fragCoord+vec2(1.0, 0.0))/u_textureSize).x;
+ float w = texture2D(u_velocity, (fragCoord+vec2(-1.0, 0.0))/u_textureSize).x;
+
+ gl_FragColor = vec4(u_halfReciprocalDx*(e-w + n-s), 0, 0, 0);
+ }
+ </script>
+
<script id="forceShader" type="x-shader/x-fragment">
precision mediump float;
@@ -59,10 +83,11 @@
}
</script>
- <script id="diffuseShader" type="x-shader/x-fragment">
+ <script id="jacobiShader" type="x-shader/x-fragment">
precision mediump float;
- uniform sampler2D u_material;
+ uniform sampler2D u_b;
+ uniform sampler2D u_x;
uniform vec2 u_textureSize;
@@ -73,20 +98,20 @@
vec2 fragCoord = gl_FragCoord.xy;
- vec2 currentState = texture2D(u_material, fragCoord/u_textureSize).xy;
+ vec2 currentState = texture2D(u_b, fragCoord/u_textureSize).xy;
//implicitly solve diffusion via jacobi iteration
- vec2 n = texture2D(u_material, (fragCoord+vec2(0.0, 1.0))/u_textureSize).xy;
- vec2 s = texture2D(u_material, (fragCoord+vec2(0.0, -1.0))/u_textureSize).xy;
- vec2 e = texture2D(u_material, (fragCoord+vec2(1.0, 0.0))/u_textureSize).xy;
- vec2 w = texture2D(u_material, (fragCoord+vec2(-1.0, 0.0))/u_textureSize).xy;
+ vec2 n = texture2D(u_x, (fragCoord+vec2(0.0, 1.0))/u_textureSize).xy;
+ vec2 s = texture2D(u_x, (fragCoord+vec2(0.0, -1.0))/u_textureSize).xy;
+ vec2 e = texture2D(u_x, (fragCoord+vec2(1.0, 0.0))/u_textureSize).xy;
+ vec2 w = texture2D(u_x, (fragCoord+vec2(-1.0, 0.0))/u_textureSize).xy;
vec2 nextState = (n + s + e + w + u_alpha * currentState) * u_reciprocalBeta;
gl_FragColor = vec4(nextState, 0, 0);
}
- </script>
+ </script>
<script id="advectShader" type="x-shader/x-fragment">
precision mediump float;
diff --git a/main.js b/main.js
index bda07e2..f19f610 100755
--- a/main.js
+++ b/main.js
@@ -46,17 +46,23 @@ function initGL() {
GPU.setUniformForProgram("advect", "u_velocity", 0, "1i");
GPU.setUniformForProgram("advect", "u_material", 1, "1i");
+ GPU.createProgram("diverge", "2d-vertex-shader", "divergenceShader");
+ GPU.setUniformForProgram("diverge" ,"u_textureSize", [width, height], "2f");
+ GPU.setUniformForProgram("diverge", "u_halfReciprocalDx", 1/(2*dx), "1f");
+ GPU.setUniformForProgram("diverge", "u_velocity", 0, "1i");
+
GPU.createProgram("force", "2d-vertex-shader", "forceShader");
GPU.setUniformForProgram("force" ,"u_textureSize", [width, height], "2f");
GPU.setUniformForProgram("force", "u_dt", dt, "1f");
GPU.setUniformForProgram("force", "u_velocity", 0, "1i");
- GPU.createProgram("diffuse", "2d-vertex-shader", "diffuseShader");
- GPU.setUniformForProgram("diffuse" ,"u_textureSize", [width, height], "2f");
+ GPU.createProgram("jacobi", "2d-vertex-shader", "jacobiShader");
+ GPU.setUniformForProgram("jacobi" ,"u_textureSize", [width, height], "2f");
var alpha = dx*dx/(nu*dt);
- GPU.setUniformForProgram("diffuse", "u_alpha", alpha, "1f");
- GPU.setUniformForProgram("diffuse", "u_reciprocalBeta", 1/(4+alpha), "1f");
- GPU.setUniformForProgram("diffuse", "u_material", 0, "1i");
+ GPU.setUniformForProgram("jacobi", "u_alpha", alpha, "1f");
+ GPU.setUniformForProgram("jacobi", "u_reciprocalBeta", 1/(4+alpha), "1f");
+ GPU.setUniformForProgram("jacobi", "u_b", 0, "1i");
+ GPU.setUniformForProgram("jacobi", "u_x", 1, "1i");
GPU.createProgram("render", "2d-vertex-shader", "2d-render-shader");
GPU.setUniformForProgram("render" ,"u_textureSize", [width, height], "2f");
@@ -83,8 +89,8 @@ function render(){
GPU.step("advect", ["velocity", "velocity"], "nextVelocity");//advect velocity
GPU.swapTextures("velocity", "nextVelocity");
for (var i=0;i<1;i++){
- GPU.step("diffuse", ["velocity"], "nextVelocity");//diffuse velocity
- GPU.step("diffuse", ["nextVelocity"], "velocity");//diffuse velocity
+ GPU.step("jacobi", ["velocity", "velocity"], "nextVelocity");//diffuse velocity
+ GPU.step("jacobi", ["nextVelocity", "nextVelocity"], "velocity");//diffuse velocity
}
GPU.setProgram("force");
if (mouseEnable){
@@ -98,6 +104,14 @@ function render(){
GPU.step("force", ["velocity"], "nextVelocity");
GPU.swapTextures("velocity", "nextVelocity");
+ //compute pressure
+ GPU.step("diverge", ["velocity"], "velocityDivergence");//calc velocity divergence
+ for (var i=0;i<3;i++){
+ GPU.step("jacobi", ["velocityDivergence", "pressure"], "nextPressure");//diffuse velocity
+ GPU.step("jacobi", ["velocityDivergence", "nextPressure"], "pressure");//diffuse velocity
+ }
+
+ //subtract pressure gradient
// GPU.step("diffuse", ["material"], "nextMaterial");
GPU.step("advect", ["velocity", "material"], "nextMaterial");
@@ -130,17 +144,18 @@ function resetWindow(){
GPU.setSize(width, height);
var velocity = new Float32Array(width*height*4);
- for (var i=0;i<height;i++){
- for (var j=0;j<width;j++){
- var index = 4*(i*width+j);
- // velocity[index] = i/1000;
- // velocity[index+1] = j/1000;
- }
- }
GPU.initTextureFromData("velocity", width, height, "FLOAT", velocity, true);
GPU.initFrameBufferForTexture("velocity");
GPU.initTextureFromData("nextVelocity", width, height, "FLOAT", new Float32Array(width*height*4), true);
GPU.initFrameBufferForTexture("nextVelocity");
+
+ GPU.initTextureFromData("velocityDivergence", width, height, "FLOAT", new Float32Array(width*height*4), true);
+ GPU.initFrameBufferForTexture("velocityDivergence");
+ GPU.initTextureFromData("pressure", width, height, "FLOAT", new Float32Array(width*height*4), true);
+ GPU.initFrameBufferForTexture("pressure");
+ GPU.initTextureFromData("nextPressure", width, height, "FLOAT", new Float32Array(width*height*4), true);
+ GPU.initFrameBufferForTexture("nextPressure");
+
var material = new Float32Array(width*height*4);
for (var i=0;i<height;i++){
for (var j=0;j<width;j++){
--
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