Home
Blogs
Forums
News
Portfolios
Projects
Tutorials
30 users logged in
New? Learn about game development.
Before posting, review our community guidelines.
Follow Us
Chat in the GameDev.net Discord!
Mastodon
Back to Graphics and GPU Programming

projective texture mapping

Started by
-1 comments, last by Neutrinohunter 16 years, 6 months ago
I have recently been trying to implement some shadowing algorithms and have come unstuck trying to implement this one. The algorithm I have gathered (from various nvidia, ATI and here) for it is: -Set up an orthographic projection -Resize the viewport so that the entire terrain is within the viewing window -Transform the scene using the light's direction vector -Render all scene meshes to the screen -Copy frame buffer to a texture -Reset modelview transformation to look straight down at terrain -Render terrain using the texture we just created -Copy frame buffer to final shadow map texture making use of Render To Texture availability inside OpenGL. I have been following an example which is similar to what I want but I can't see what it wrong with my code: http://gpwiki.org/index.php/Generating_Mesh_Shadows_On_Terrain_Using_OpenGL I only seem to be getting a red quad in the bottom left hand corner of the screen and I'm not sure why. 
void createProjectiveTexture(JVector3D lightDir) {

   //create an Image
   GLuint shadowChunk;
   glGenTextures(1, &shadowChunk);
   glBindTexture(GL_TEXTURE_2D, shadowChunk);
   glEnable(GL_TEXTURE_2D);
   glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 0, 0,0, 256, 256);
   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

   //Set up an Orthographic Projection
   //Ensure the whole scene is withing the viewing window
   const int TEXTURE_MAP_SIZE = 512;
   glViewport(0, 0, TEXTURE_MAP_SIZE,TEXTURE_MAP_SIZE);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0, TEXTURE_MAP_SIZE, 0, TEXTURE_MAP_SIZE, -10000, 10000);
   glMatrixMode(GL_MODELVIEW);

   //Transform the scee using light vector
   JVector3D lookAt(0,0,0);
   JVector3D up(0,1,0);
   gluLookAtv(lightDir, lookAt, up);

   //Render the Scene
   
 //  drawLightSource();
//   drawFloor();
//   drawBoundingScene();


   //make sure the vertices are inside for some reason they are not
   //at the moment

   static GLint viewport[4];
   static GLdouble modelview[16];
   static GLdouble projection[16];
   static GLfloat winX, winY, winZ;
   
   float minX = 999999, maxX = -999999;
   float minY = 999999, maxY = -999999;
   double X, Y, Z;

   glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
   glGetDoublev( GL_PROJECTION_MATRIX, projection );
   glGetIntegerv( GL_VIEWPORT, viewport );

//   renderVertex(-100.0,0.0,100.0);
//      glTexCoord2f(0.0,5.0);renderVertex(100.0,0.0,100.0);
//      glTexCoord2f(5.0,5.0);renderVertex(100.0,0.0,-100.0);
//      glTexCoord2f(5.0,0.0);renderVertex(-100.0,0.0,-100.0);
   gluProject(100.0,0.0,100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;

   gluProject(100.0,0.0,-100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;
   gluProject(-100.0,0.0,-100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;
   gluProject(-100.0,0.0,100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;
   
   static float minX2, minY2, maxX2, maxY2;
                     minX2 = minX;
                     minY2 = minY;
                     maxX2 = maxX;
                     maxY2 = maxY;

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
   glViewport(0, 0, TEXTURE_MAP_SIZE,TEXTURE_MAP_SIZE);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(minX, maxX, minY, maxY, -10000, 10000);
   glMatrixMode(GL_MODELVIEW);

//   glColorMask(false, false, false, false);
//   glColorMask(true, true, true, true);
  //glColor3f(0.0,0.0,0.0);
    drawLightSource();
    drawFloor();
    drawBoundingScene();
    drawScene(true, false, PROJECTED_TEXTURE);
   
   //Use Render to Texture
   glBindTexture(GL_TEXTURE_2D, shadowChunk); 
   glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, TEXTURE_MAP_SIZE, TEXTURE_MAP_SIZE);
   glBindTexture(GL_TEXTURE_2D, 0);
   //Reset View Position to be above the center (0,0,0) along the Y Axis.
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
   glViewport(0, 0, TEXTURE_MAP_SIZE, TEXTURE_MAP_SIZE);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0, 0, TEXTURE_MAP_SIZE, TEXTURE_MAP_SIZE, -10000, 10000);
   glMatrixMode(GL_MODELVIEW);

   glLoadIdentity();
   glRotatef(90.0f, 1, 0, 0);       //Rotate so XZ becomes XY

   minX = minY = 999999;
   maxX = maxY = -999999;


   glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
   glGetDoublev( GL_PROJECTION_MATRIX, projection );
   glGetIntegerv( GL_VIEWPORT, viewport );

//   renderVertex(-100.0,0.0,100.0);
//      glTexCoord2f(0.0,5.0);renderVertex(100.0,0.0,100.0);
//      glTexCoord2f(5.0,5.0);renderVertex(100.0,0.0,-100.0);
//      glTexCoord2f(5.0,0.0);renderVertex(-100.0,0.0,-100.0);
   gluProject(100.0,0.0,100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;

   gluProject(100.0,0.0,-100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;
   gluProject(-100.0,0.0,-100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;
   gluProject(-100.0,0.0,100.0, modelview, projection, viewport, &X, &Y, &Z);
   if(X < minX) minX = X; if(X > maxX) maxX = X; if(Y < minY) minY = Y;
   if(Y > maxY) maxY = Y;

   glViewport(0, 0, 256,256);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(minX, minY, maxX, maxY, -10000, 10000);
   glMatrixMode(GL_MODELVIEW);
   // rotate view so that xz plane becomes the xy plane
   glLoadIdentity();
   glRotatef(90.0f, 1, 0, 0);

   //Set up projective Texturing and Planes
   float PS[] = {1, 0, 0, 0};
   float PT[] = {0, 1, 0, 0};
   float PR[] = {0, 0, 1, 0};
   float PQ[] = {0, 0, 0, 1};
   
   glTexGenfv(GL_S, GL_EYE_PLANE, PS);
   glTexGenfv(GL_T, GL_EYE_PLANE, PT);
   glTexGenfv(GL_R, GL_EYE_PLANE, PR);
   glTexGenfv(GL_Q, GL_EYE_PLANE, PQ);
   
   glEnable(GL_TEXTURE_GEN_S);
   glEnable(GL_TEXTURE_GEN_T);
   glEnable(GL_TEXTURE_GEN_R);
   glEnable(GL_TEXTURE_GEN_Q);
   glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   
   glBindTexture(GL_TEXTURE_2D, shadowChunk);

   glMatrixMode(GL_TEXTURE);
   glLoadIdentity();
   glTranslatef(0.5, 0.5, 0);
   glScalef(0.5, 0.5, 1);
   glOrtho(minX2, maxX2, minY2, maxY2, -10000, 10000);
   gluLookAtv(v_LightSource, lookAt, up);
   glMatrixMode(GL_MODELVIEW);
   drawScene(false, false, PROJECTED_TEXTURE);

   //copy final image into texture

   glBindTexture(GL_TEXTURE_2D, shadowChunk);
   glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, TEXTURE_MAP_SIZE, TEXTURE_MAP_SIZE);

   // disable TexGEN - projective texturing
   glDisable(GL_TEXTURE_GEN_S);
   glDisable(GL_TEXTURE_GEN_T);
   glDisable(GL_TEXTURE_GEN_R);
   glDisable(GL_TEXTURE_GEN_Q);

   glMatrixMode(GL_TEXTURE);
   glLoadIdentity();
   
   glMatrixMode(GL_MODELVIEW);
}
Anybody have any ideas what could be the problem? Neutrinohunter Edit: In Code!

This topic is closed to new replies.

Advertisement

Popular Topics

Aybe One
How do you manage yourself and your time as years pass on? GDNet Lounge
Jikoob
Too many managers? General and Gameplay Programming
ReignOnU
Do your part to stop global warming and climate change GDNet Lounge
aigan
The promise of freedom in story games Game Design and Theory
robertrobert
Facebook Ads for sales on steam, does it work? Games Business and Law
AliAbdulKareem
Understanding the wavy-like shape in alpha-testing magnification for text rendering Graphics and GPU Programming
Advertisement

Recommended Tutorials

GameDev.net
How to nurture a holistic, proactive, approach to technology problem-solving Networking and Multiplayer
Myopic Rhino
The P5 Basics, and the New Profiling Registers General and Gameplay Programming
gdarchive
How to Make Accurate Time Estimates Production and Management
Myopic Rhino
Paris GDC Highlights Event Coverage
mrluisp
Simple C++ Event Handling General and Gameplay Programming

Reticulating splines

About GameDev.net
Community Guidelines
Terms of Service
Privacy Policy
Contact Us
Copyright (c) 1999-2024 GameDev.net, LLC
Back to Top