Deferred Shading by OpenGL

It is quite popular to use deferred shading and not standard shading these days. A lot of the details already described well with pros and cons.
With many lights and vertices - worth to check and I have seen already 5.8x better results for deferred approach: Def: 480FPS vs Std: 84FPS for 1081344 vertices
Based on the model(s): Harley Quinn contains a bit more than 36K vertices alone.
Where from the OpenGL side, differences are (Left is deferred shading):

First Text Fragment Second Text Fragment

1 //Pass 1 2 //Draw the geometry, saving parameters into the buffer 3 4 //Make the pbuffer the current context 5 pbuffer.MakeCurrent(); 6 7 //Clear buffers 8 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 9 glColor4f(1.0f, 1.0f, 1.0f, 1.0f); 10 11 glLoadIdentity(); 12 gluLookAt( 0.0f, 4.0f, 3.0f, 13 0.0f, 0.0f, 0.0f, 14 0.0f, 1.0f, 0.0f); 15 16 //Bind and enable vertex & fragment programs 17 glBindProgramARB(GL_VERTEX_PROGRAM_ARB, deferredShadingPass1VP); 18 glEnable(GL_VERTEX_PROGRAM_ARB); 19 20 glBindProgramNV(GL_FRAGMENT_PROGRAM_NV, deferredShadingPass1FP); 21 glEnable(GL_FRAGMENT_PROGRAM_NV); 22 23 //Draw the torus knot 24 glDrawElements(GL_TRIANGLES, torusKnot.numIndices, GL_UNSIGNED_INT, (char *)NULL); 25 26 //Draw the "floor" 27 glNormal3f(0.0f, 1.0f, 0.0f); 28 glBegin(GL_TRIANGLE_STRIP); 29 { 30 glVertex3f( 5.0f,-0.5f, 5.0f); 31 glVertex3f( 5.0f,-0.5f,-5.0f); 32 glVertex3f(-5.0f,-0.5f, 5.0f); 33 glVertex3f(-5.0f,-0.5f,-5.0f); 34 } 35 glEnd(); 36 37 glDisable(GL_VERTEX_PROGRAM_ARB); 38 glDisable(GL_FRAGMENT_PROGRAM_NV); 39 40 //Copy the pbuffer contents into the pbuffer texture 41 glBindTexture(GL_TEXTURE_RECTANGLE_NV, pbufferTexture); 42 glCopyTexSubImage2D(GL_TEXTURE_RECTANGLE_NV, 0, 0, 0, 0, 0, 43 pbuffer.width, pbuffer.height); 44 45 //Make the window the current context 46 WINDOW::Instance()->MakeCurrent(); 47 48 //Pass 2 49 //Draw a quad covering the region of influence of each light 50 //Unpack the data from the buffer, perform the lighting equation and update 51 //the framebuffer 52 53 //Set orthographic projection, 1 unit=1 pixel 54 glMatrixMode(GL_PROJECTION); 55 glPushMatrix(); 56 glLoadIdentity(); 57 gluOrtho2D(0, WINDOW::Instance()->width, 0, WINDOW::Instance()->height); 58 59 //Set identity modelview 60 glMatrixMode(GL_MODELVIEW); 61 glPushMatrix(); 62 glLoadIdentity(); 63 64 //Disable depth test 65 glDisable(GL_DEPTH_TEST); 66 67 //Bind the pbuffer texture 68 glBindTexture(GL_TEXTURE_RECTANGLE_NV, pbufferTexture); 69 70 //Bind and enable fragment program 71 glBindProgramNV(GL_FRAGMENT_PROGRAM_NV, deferredShadingPass2FP); 72 glEnable(GL_FRAGMENT_PROGRAM_NV); 73 74 //Loop through the lights 75 for(int i=0; i<numLights; i) 76 { 77 //Calculate the rectangle to draw for this light 78 int rectX, rectY, rectWidth, rectHeight; 79 80 lights[i].GetWindowRect(WINDOW::Instance()->width, WINDOW::Instance()->height, 81 viewMatrix, currentTime, cameraNearDistance, 82 cameraFovy, cameraAspectRatio, 83 rectX, rectY, rectWidth, rectHeight); 84 85 //Enable additive blend if i>0 86 if(i>0) 87 { 88 glBlendFunc(GL_ONE, GL_ONE); 89 glEnable(GL_BLEND); 90 } 91 92 //Send the light's color to fragment program local parameter 0 93 glProgramLocalParameter4fvARB( GL_FRAGMENT_PROGRAM_NV, 0, lights[i].color); 94 95 //Send 1/(light radius)^2 to fragment program local parameter 1 96 float inverseSquareLightRadius=1.0f/(lights[i].radius*lights[i].radius); 97 glProgramLocalParameter4fARB( GL_FRAGMENT_PROGRAM_NV, 1, 98 inverseSquareLightRadius, inverseSquareLightRadius, 99 inverseSquareLightRadius, inverseSquareLightRadius); 100 101 //Send the light's position to fragment program local parameter 2 102 glProgramLocalParameter4fvARB( GL_FRAGMENT_PROGRAM_NV, 2, 103 VECTOR4D(lights[i].GetPosition(currentTime))); 104 105 //Draw the rectangle 106 glBegin(GL_TRIANGLE_STRIP); 107 { 108 glVertex2i(rectX, rectY); 109 glVertex2i(rectX rectWidth, rectY); 110 glVertex2i(rectX, rectY rectHeight); 111 glVertex2i(rectX rectWidth, rectY rectHeight); 112 } 113 glEnd(); 114 } 115 116 //Restore matrices 117 glMatrixMode(GL_PROJECTION); 118 glPopMatrix(); 119 glMatrixMode(GL_MODELVIEW); 120 glPopMatrix(); 121 122 glEnable(GL_DEPTH_TEST); 123 glDisable(GL_FRAGMENT_PROGRAM_NV); 124 glDisable(GL_BLEND); 125 1 //Make an initial pass to lay down Z 2 glColorMask(0, 0, 0, 0); 3 4 //Draw the torus knot 5 glDrawElements(GL_TRIANGLES, torusKnot.numIndices, GL_UNSIGNED_INT, (char *)NULL); 6 7 //Draw the "floor" 8 glNormal3f(0.0f, 1.0f, 0.0f); 9 glBegin(GL_TRIANGLE_STRIP); 10 { 11 glVertex3f( 5.0f,-0.5f, 5.0f); 12 glVertex3f( 5.0f,-0.5f,-5.0f); 13 glVertex3f(-5.0f,-0.5f, 5.0f); 14 glVertex3f(-5.0f,-0.5f,-5.0f); 15 } 16 glEnd(); 17 18 glColorMask(1, 1, 1, 1); 19 20 //Bind and enable vertex & fragment programs 21 glBindProgramARB(GL_VERTEX_PROGRAM_ARB, standardShadingVP); 22 glEnable(GL_VERTEX_PROGRAM_ARB); 23 24 glBindProgramARB(GL_FRAGMENT_PROGRAM_ARB, standardShadingFP); 25 glEnable(GL_FRAGMENT_PROGRAM_ARB); 26 27 //Loop through the lights 28 for(int i=0; i<numLights; i) 29 { 30 //Calculate and set the scissor rectangle for this light 31 int scissorX, scissorY, scissorWidth, scissorHeight; 32 33 lights[i].GetWindowRect(WINDOW::Instance()->width, WINDOW::Instance()->height, 34 viewMatrix, currentTime, cameraNearDistance, 35 cameraFovy, cameraAspectRatio, 36 scissorX, scissorY, scissorWidth, scissorHeight); 37 38 glScissor(scissorX, scissorY, scissorWidth, scissorHeight); 39 glEnable(GL_SCISSOR_TEST); 40 41 //Enable additive blend if i>0 42 if(i>0) 43 { 44 glBlendFunc(GL_ONE, GL_ONE); 45 glEnable(GL_BLEND); 46 } 47 48 //Calculate the object space light position and send to 49 //vertex program local parameter 0 50 //Object space and world space are the same 51 glProgramLocalParameter4fvARB( GL_VERTEX_PROGRAM_ARB, 0, 52 VECTOR4D(lights[i].GetPosition(currentTime))); 53 54 //Send the light's color to fragment program local parameter 0 55 glProgramLocalParameter4fvARB( GL_FRAGMENT_PROGRAM_ARB, 0, lights[i].color); 56 57 //Send 1/(light radius)^2 to fragment program local parameter 1 58 float inverseSquareLightRadius=1.0f/(lights[i].radius*lights[i].radius); 59 glProgramLocalParameter4fARB( GL_FRAGMENT_PROGRAM_ARB, 1, 60 inverseSquareLightRadius, inverseSquareLightRadius, 61 inverseSquareLightRadius, inverseSquareLightRadius); 62 63 //Draw the torus knot 64 glDrawElements(GL_TRIANGLES, torusKnot.numIndices, GL_UNSIGNED_INT, (char *)NULL); 65 66 //Draw the "floor" 67 glNormal3f(0.0f, 1.0f, 0.0f); 68 glBegin(GL_TRIANGLE_STRIP); 69 { 70 glVertex3f( 5.0f,-0.5f, 5.0f); 71 glVertex3f( 5.0f,-0.5f,-5.0f); 72 glVertex3f(-5.0f,-0.5f, 5.0f); 73 glVertex3f(-5.0f,-0.5f,-5.0f); 74 } 75 glEnd(); 76 } 77 78 glDisable(GL_VERTEX_PROGRAM_ARB); 79 glDisable(GL_FRAGMENT_PROGRAM_ARB); 80 glDisable(GL_SCISSOR_TEST); 81 glDisable(GL_BLEND);

Number of differences: 10 Added(5,22) Deleted(0,48) Changed(82) Changed in changed(42) Ignored Select Diff

Shaders side will be later...

PS have you seen a good difference viewer ?