Implement multi-pass postprocessing shader.

This allows attaching multiple shader programs, processing the entire
screen as texture. Chaining shaders works, each shader will use
the output of the previous shader as input.

BBGE/AfterEffect.cpp

@@ -63,6 +63,28 @@ AfterEffectManager::AfterEffectManager(int xDivs, int yDivs)
 
 void AfterEffectManager::loadShaders()
 {
+	deleteShaders();
+
+	Shader *sh = new Shader();
+	sh->load("data/shaders/test.vert", "data/shaders/test.frag");
+	if(sh->isLoaded())
+		scriptShader[0] = sh;
+	else
+		delete sh;
+
+	sh = new Shader();
+	sh->load("data/shaders/test2.vert", "data/shaders/test2.frag");
+	if(sh->isLoaded())
+		scriptShader[1] = sh;
+	else
+		delete sh;
+
+	sh = new Shader();
+	sh->load("data/shaders/test3.vert", "data/shaders/test3.frag");
+	if(sh->isLoaded())
+		scriptShader[2] = sh;
+	else
+		delete sh;
 }
 
 AfterEffectManager::~AfterEffectManager()
@@ -77,6 +99,7 @@ AfterEffectManager::~AfterEffectManager()
 		delete[] drawGrid;
 	}
 	deleteEffects();
+	deleteShaders();
 }
 
 void AfterEffectManager::deleteEffects()
@@ -94,6 +117,18 @@ void AfterEffectManager::deleteEffects()
 		openSpots.pop();
 }
 
+void AfterEffectManager::deleteShaders()
+{
+	for(size_t i = 0; i < scriptShader.size(); ++i)
+	{
+		if(scriptShader[i])
+		{
+			delete scriptShader[i];
+			scriptShader[i] = 0;
+		}
+	}
+}
+
 void AfterEffectManager::clear()
 {
 	deleteEffects();
@@ -149,24 +184,18 @@ void AfterEffectManager::destroyEffect(int id)
 
 void AfterEffectManager::render()
 {
+	assert(core->frameBuffer.isInited());
+
 #ifdef BBGE_BUILD_OPENGL
 	glPushMatrix();
-	//glDisable(GL_BLEND);
-	//glEnable(GL_BLEND);
-	//glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	//glBlendFunc(GL_SRC_ALPHA, GL_ONE);
+
 	glDisable (GL_ALPHA_TEST);
 	glDisable(GL_BLEND);
 
 	core->frameBuffer.endCapture();
 	glTranslatef(core->cameraPos.x, core->cameraPos.y, 0);
 	glScalef(core->invGlobalScale, core->invGlobalScale,0);
-	/*
-	static float angle;
-	angle += 0.03f;
-	*/
-	//glRotatef(angle, 0, 0, 1);
-	//glColor4f(1,1,1,0.75);
+
 	glColor4f(1,1,1,1);
 	renderGrid();
 	//renderGridPoints();
@@ -178,78 +207,45 @@ void AfterEffectManager::renderGrid()
 {
 #ifdef BBGE_BUILD_OPENGL
 
-
-	int shadersOn = 0;
 	int firstShader = -1;
 	int lastShader = -1;
+	Shader *activeShader = 0;
 	for (size_t i = 0; i < scriptShader.size(); ++i)
 	{
 		if(scriptShader[i])
 		{
-			++shadersOn;
 			if(firstShader < 0)
+			{
 				firstShader = i;
+				activeShader = scriptShader[i];
+			}
 			lastShader = i;
 		}
 	}
 
-	if (core->frameBuffer.isInited())
-		core->frameBuffer.bindTexture();
-
-	Shader *activeShader=0;
-	if (core->frameBuffer.isInited())
-	{
-		if(scriptShader.size() && scriptShader[0])
-			activeShader = scriptShader[0];
-
-	}
-
-	if (activeShader)
-	{
-		//while(glGetError() != GL_NO_ERROR) {}
-
-		activeShader->bind();
-
-		activeShader->setInt("tex", 0);
-	}
-
 	screenWidth = core->getWindowWidth();
 	screenHeight = core->getWindowHeight();
 
-	/*
-	float percentX, percentY;
-	percentX = 1;
-	percentY = 0.5;
-	*/
-
-	/*
-	percentX = (float)textureWidth/(float)screenWidth;
-	percentY = (float)textureHeight/(float)screenHeight;
-	*/
-
 	float percentX, percentY;
 	percentX = (float)screenWidth/(float)textureWidth;
 	percentY = (float)screenHeight/(float)textureHeight;
 
-
-		/*
-		if (screenWidth <= textureWidth)
-		{
-			percentX = (float)screenWidth/(float)textureWidth;
-			percentY = (float)screenHeight/(float)textureHeight;
-		}
-		else
-		{
-			percentY = 10;
-		}
-		*/
-
-
 	int vw = core->getVirtualWidth();
 	int vh = core->getVirtualHeight();
 	int offx = -core->getVirtualOffX();
 	int offy = -core->getVirtualOffY();
 
+	core->frameBuffer.bindTexture();
+
+	if(activeShader)
+	{
+		activeShader->bind();
+		activeShader->setInt("tex", 0);
+
+		if(firstShader != lastShader)
+			backupBuffer.startCapture();
+	}
+
 	//float div = xDivs;
 	for (int i = 0; i < (xDivs-1); i++)
 	{
@@ -283,32 +279,48 @@ void AfterEffectManager::renderGrid()
 	float width2 = float(vw)/2;
 	float height2 = float(vh)/2;
 
-	/*
-	for(size_t i = 1; i < scriptShader.size(); ++i)
+
+	if(firstShader != lastShader)
 	{
-		if(scriptShader[i])
+		// From here on: secondary shader passes.
+		// We just outputted to the backup buffer...
+		FrameBuffer *fbIn = &core->frameBuffer;
+		FrameBuffer *fbOut = &backupBuffer;
+
+
+		for(int i = firstShader + 1; i <= lastShader; ++i)
 		{
-			if (core->frameBuffer.isInited())
-				core->frameBuffer.startCapture();
+			activeShader = scriptShader[i];
+			if(!activeShader)
+				continue;
+
+			// Swap and exchange framebuffers. The old output buffer serves as texture input for the other one
+			fbOut->endCapture();
+			std::swap(fbIn, fbOut);
+			fbIn->bindTexture();
+
+			// If this is the last pass, do not render to a frame buffer again
+			if(i != lastShader)
+				fbOut->startCapture();
+
+			activeShader->bind();
+			activeShader->setInt("tex", 0);
 			
-			scriptShader[i]->bind();
-			scriptShader[i]->setInt("tex", 0);
+			// note that offx, offy are negative here!
 			glBegin(GL_QUADS);
 				glTexCoord2d(0.0f, 0.0f);
-				glVertex3f(-width2, height2,  0.0f);
+				glVertex3f(offx, vh+offy,  0.0f);
 				glTexCoord2d(percentX, 0.0f);
-				glVertex3f( width2, height2,  0.0f);
+				glVertex3f( vw+offx, vh+offy,  0.0f);
 				glTexCoord2d(percentX, percentY);
-				glVertex3f( width2,  -height2,  0.0f);
+				glVertex3f( vw+offx,  offy,  0.0f);
 				glTexCoord2d(0.0f, percentY);
-				glVertex3f(-width2,  -height2,  0.0f);
+				glVertex3f(offx,  offy,  0.0f);
 			glEnd();
-			scriptShader[i]->unbind();
-
-			capture();
+			
+			activeShader->unbind();
 		}
 	}
-	*/
 
 
 	// uncomment to render grid points
@@ -377,6 +389,7 @@ void AfterEffectManager::renderGridPoints()
 void AfterEffectManager::unloadDevice()
 {
 	backupBuffer.unloadDevice();
+	deleteShaders();
 }
 
 void AfterEffectManager::reloadDevice()
@@ -401,6 +414,8 @@ void AfterEffectManager::reloadDevice()
 		backupBuffer.reloadDevice();
 	else
 		backupBuffer.init(-1, -1, true);
+
+	loadShaders();
 }
 
 void AfterEffectManager::addEffect(Effect *e)

BBGE/AfterEffect.h

@@ -91,6 +91,7 @@ public:
 	void renderGridPoints();
 
 	void loadShaders();
+	void deleteShaders();
 
 	void unloadDevice();
 	void reloadDevice();

BBGE/Shader.cpp

@@ -192,6 +192,13 @@ unsigned int Shader::_compileShader(int type, const char *src, char *errbuf, siz
 #ifdef BBGE_BUILD_SHADERS
 	GLint compiled = 0;
 	GLhandleARB handle = glCreateShaderObjectARB(type);
+	if(!handle)
+	{
+		std::ostringstream os;
+		os << "Failed to create shader object of type " << type;
+		debugLog(os.str());
+		return 0;
+	}
 
 	glShaderSourceARB( handle, 1, &src, NULL );
 	glCompileShaderARB( handle);