From e516095a425d1c8d5bd9f9004416a6c19bcaf84f Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Fri, 25 May 2018 19:49:37 +0200
Subject: Dynamically build compute shader from field function

---
 src/main.cc             | 16 ++++++++++++++--
 src/shader/compute.glsl | 11 ++---------
 2 files changed, 16 insertions(+), 11 deletions(-)

(limited to 'src')

diff --git a/src/main.cc b/src/main.cc
index ceffe67..71d1cbd 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -22,7 +22,7 @@
 #include "shader/display_vertex.glsl"
 #include "shader/display_fragment.glsl"
 
-const unsigned int particle_count = 1000;
+const unsigned int particle_count = 2500;
 const unsigned int max_ups        = 100;
 const unsigned int texture_count  = 20;
 
@@ -83,6 +83,13 @@ std::vector<GLfloat> makeInitialParticles(std::size_t count) {
 	return buffer;
 }
 
+std::string getShaderFunction(const std::string& fx, const std::string& fy) {
+	return COMPUTE_SHADER_CODE
+	    + "vec2 f(vec2 v) {"
+	    +     "return vec2(" + fx + "," + fy + ");"
+	    + "}";
+}
+
 int main() {
 	if( !glfwInit() ) {
 		std::cerr <<  "Failed to initialize GLFW" << std::endl;
@@ -123,7 +130,12 @@ int main() {
 
 	GraphicShader sceneShader(VERTEX_SHADER_CODE, FRAGMENT_SHADER_CODE);
 
-	ComputeShader computeShader(COMPUTE_SHADER_CODE);
+	ComputeShader computeShader(
+		getShaderFunction(
+			"cos(v.x*sin(v.y))",
+			"sin(v.x-v.y)"
+		)
+	);
 	computeShader.workOn(particleBuffer->getBuffer());
 
 	GraphicShader displayShader(DISPLAY_VERTEX_SHADER_CODE,
diff --git a/src/shader/compute.glsl b/src/shader/compute.glsl
index 148157b..eaf5579 100644
--- a/src/shader/compute.glsl
+++ b/src/shader/compute.glsl
@@ -6,17 +6,10 @@ layout (std430, binding=1) buffer bufferA{ float data[]; };
 
 uniform vec2 world;
 
-// vector field definition
-
-vec2 f(vec2 v) {
-	return vec2(
-		cos(v.x*sin(v.y)),
-		sin(v.x-v.y)
-	);
-}
-
 // ODE solver
 
+vec2 f(vec2); // field definition is to be appended
+
 vec2 explicitEuler(float h, vec2 v) {
 	return v + h * f(v);
 }
-- 
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