Here’s a small snippet to compute water caustics for a given depth:
Result:
It’s far from beeing perfect, there is some blur missing, but it’s more a concept than a final solution.
All computation is done on the GPU using compute shaders.
Code:
from panda3d.core import *
loadPrcFileData("", """
win-size 512 512
""")
import direct.directbase.DirectStart
resultTex = Texture("result")
resultTex.setup2dTexture(512, 512, Texture.TFloat, Texture.FRgba)
tempTex = Texture("temp")
tempTex.setup2dTexture(512, 512, Texture.TInt, Texture.FR32)
sourceTex = loader.loadTexture("source.png")
sourceTex.setMinfilter(Texture.FTLinear)
sourceTex.setMagfilter(Texture.FTLinear)
sourceTex.setWrapU(Texture.WMRepeat)
sourceTex.setWrapV(Texture.WMRepeat)
tempDispTex = Texture("tempDisp")
tempDispTex.setup2dTexture(512, 512, Texture.TFloat, Texture.FRgba)
clearTexture = """
#version 430
layout (local_size_x = 16, local_size_y = 16) in;
uniform writeonly iimage2D dest;
uniform writeonly image2D tempDisplace;
uniform sampler2D source;
uniform float frameTime;
void main() {
ivec2 texelCoords = ivec2(gl_GlobalInvocationID.xy);
imageStore(dest, texelCoords, ivec4(0));
vec2 texcoord = vec2(texelCoords) / 512.0;
float speed = 0.2;
float tspeed = frameTime * speed;
float h0 = texture(source, texcoord*0.1 + tspeed * vec2(0.04, 0.03)).x;
float h1 = texture(source, texcoord*0.15 - tspeed * vec2(0.05, -0.07)).x;
float h2 = texture(source, texcoord*0.2 - tspeed * vec2(0.02, 0.08)).x;
float h3 = texture(source, texcoord*0.25 - tspeed * vec2(-0.09, 0.03)).x;
float h = (h0 + h1 + h2 + h3) * 0.25;
imageStore(tempDisplace, texelCoords, vec4(h));
}
"""
computeCaustics = """
#version 430
layout (local_size_x = 16, local_size_y = 16) in;
uniform sampler2D source;
layout(r32i) uniform iimage2D dest;
void main() {
vec2 texelCoords = vec2(gl_GlobalInvocationID.xy) / 4096.0;
float h0 = texture(source, texelCoords).x;
float hx = texture(source, texelCoords + vec2(1.0/512.0,0)).x;
float hy = texture(source, texelCoords + vec2(0,1.0/512.0)).x;
vec3 normal = normalize(vec3(h0 - hx, h0 - hy, 16.0 / 512.0));
vec3 sunVector = normalize(vec3(1,1,1));
vec3 refractVector = refract(sunVector, normal, 0.1);
vec3 refractStart = vec3(texelCoords * 512.0, 0);
vec3 refractEnd = refractStart + refractVector * 50.0;
ivec2 storeCoords = ivec2(round(fract(refractEnd / 512.0) * 512.0));
imageAtomicAdd(dest, storeCoords, 1);
}
"""
convertCaustics = """
#version 430
layout (local_size_x = 16, local_size_y = 16) in;
layout(r32i) uniform iimage2D source;
uniform writeonly image2D dest;
void main() {
ivec2 texelCoords = ivec2(gl_GlobalInvocationID.xy);
int result = imageLoad(source, texelCoords).x;
//result = max(40, result);
//result -= 40;
imageStore(dest, texelCoords, vec4(vec3(result) / 255.0,1.0));
}
"""
computeCausticsShader = Shader.makeCompute(Shader.SLGLSL, computeCaustics)
convertCausticsShader = Shader.makeCompute(Shader.SLGLSL, convertCaustics)
clearTextureShader = Shader.makeCompute(Shader.SLGLSL, clearTexture)
def computeCaustics(task = None):
# Clear texture first
cn = NodePath("clearNode")
cn.setShader(clearTextureShader)
cn.setShaderInput("dest", tempTex)
cn.setShaderInput("tempDisplace", tempDispTex)
cn.setShaderInput("frameTime", globalClock.getFrameTime())
cn.setShaderInput("source", sourceTex)
sattr = cn.getAttrib(ShaderAttrib)
base.graphicsEngine.dispatchCompute(
(512/16, 512/16, 1), sattr, base.win.getGsg())
# Compute caustics
cn = NodePath("computeNode")
cn.setShader(computeCausticsShader)
cn.setShaderInput("dest", tempTex)
cn.setShaderInput("source", tempDispTex)
sattr = cn.getAttrib(ShaderAttrib)
base.graphicsEngine.dispatchCompute(
(4096/16, 4096/16, 1), sattr, base.win.getGsg())
# Convert caustics
cn = NodePath("convertNode")
cn.setShader(convertCausticsShader)
cn.setShaderInput("source", tempTex)
cn.setShaderInput("dest", resultTex)
sattr = cn.getAttrib(ShaderAttrib)
base.graphicsEngine.dispatchCompute(
(512/16, 512/16, 1), sattr, base.win.getGsg())
if task is not None:
return task.cont
base.addTask(computeCaustics, "computeCaustics")
# Write data
# base.graphicsEngine.extractTextureData(resultTex, base.win.getGsg())
# resultTex.write("result.png")
# Visualize data
cm = CardMaker("")
cm.setFrameFullscreenQuad()
cn = aspect2d.attachNewNode(cm.generate())
cn.setTexture(resultTex)
run()The application expects a source.png with the size of 512x512 to be in the working directory. For the screenshot above I used (rescaled to 512x512 before):
