void draw_scene ( void )
{
// clear the screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
// reset the matrix
glLoadIdentity ( );
// draw the user
user.draw ( );
glLoadIdentity ( );
/* Don't update color or depth. */
glDisable(GL_DEPTH_TEST);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
/* Draw 1 into the stencil buffer. */
glEnable(GL_STENCIL_TEST);
glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
glStencilFunc(GL_ALWAYS, 1, 0xffffffff);
/* Now drawing the floor just tags the floor pixels
as stencil value 1. */
// draw the tiles
for ( int x = 0; x < MAP_WIDTH; x++ )
{
for ( int y = 0; y < MAP_LENGTH; y++ )
{
tile[x][y].position.x = (float) x;
tile[x][y].position.y = 0.0f;
tile[x][y].position.z = (float) y;
tile[x][y].draw ( );
}
}
/* Re-enable update of color and depth. */
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glEnable(GL_DEPTH_TEST);
/* Now, only render where stencil is set to 1. */
glStencilFunc(GL_EQUAL, 1, 0xffffffff); /* draw if stencil ==1 */
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
/* Draw reflected ninja, but only where floor is. */
glPushMatrix();
glScalef(1.0, -1.0, 1.0);
// draw the user
user.draw ( );
glPopMatrix();
glDisable(GL_STENCIL_TEST);
}
Floor Reflections
Author
Hello everyone,
I read the brief article about reflections with OpenGL here at gamedev.net and am trying to include this cool looking effect into my own project.
My game uses 3-dimensional tiles ( 5 x 20 for now with each a size of 2 x 1 x 3 [some exceptions] ) - will adding the reflection to all those tiles decrease performance (a lot)?
Is the current "draw_scene ( )" funtion correct or do I have some mistake in there that I don't know of? This function makes my game first minimize and then when I maximize it, it is really slow...
For reflections, I'd say you need to draw your entire scene (more or less) two-three times more... so, take the time needed for one frame, and simply multiply by three... :D
but then again, that's the result of my engine, not facts.. hehe.
cheers!
but then again, that's the result of my engine, not facts.. hehe.
cheers!
Author
Update: It turned out that minimization thing was caused by something different... I have cleaned up the "draw_scene" function now and tested several things, but nothing has worked entirely correct yet...
This is the best version so far:
This is really slow and it draws the reflection everywhere - not only on the tile ground... So it seems like the whole stencil buffer thing is not working, but what exactly is wrong?
Thanks for your reply though - keep them coming please.
This is the best version so far:
void draw_scene ( void ){ // clear the screen glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); glEnable(GL_STENCIL_TEST); glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE); glStencilFunc(GL_ALWAYS, 1, 0xffffffff); glLoadIdentity ( ); // draw the tiles for ( int x = 0; x < MAP_WIDTH; x++ ) { for ( int y = 0; y < MAP_LENGTH; y++ ) { if ( tile[x][y].type == STANDARD ) { tile[x][y].position.x = (float) x; tile[x][y].position.y = 0.0f; tile[x][y].position.z = (float) y; tile[x][y].draw ( ); } } } glLoadIdentity ( ); glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); glStencilFunc(GL_EQUAL, 1, 0xffffffff); glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); glScalef(1.0, -1.0, 1.0); glTranslatef ( 0.0f, 5.0f, 0.0f ); glEnable(GL_BLEND ); glColor4f(1.0f,1.0f,1.0f,0.4f); glBlendFunc(GL_SRC_ALPHA,GL_ONE); user.draw ( ); glDisable(GL_BLEND); glPopMatrix(); glDisable(GL_STENCIL_TEST); glLoadIdentity ( ); user.draw ( ); glLoadIdentity ( ); // move camera behind the ball glTranslatef ( user.sphere.position.x, -CAM_HEIGHT, user.sphere.position.z ); // draw the tiles for ( x = 0; x < MAP_WIDTH; x++ ) { for ( int y = 0; y < MAP_LENGTH; y++ ) { if ( tile[x][y].type == STANDARD ) { glEnable(GL_BLEND ); glColor4f(1.0f,1.0f,1.0f,0.2f); glBlendFunc(GL_SRC_ALPHA,GL_ONE); } tile[x][y].position.x = (float) x; tile[x][y].position.y = 0.0f; tile[x][y].position.z = (float) y; tile[x][y].draw ( ); if ( tile[x][y].type == STANDARD ) { glDisable(GL_BLEND); } } }}This is really slow and it draws the reflection everywhere - not only on the tile ground... So it seems like the whole stencil buffer thing is not working, but what exactly is wrong?
Thanks for your reply though - keep them coming please.
Something you may want to do is look into drawing the scene inverted to a texture (via pbuffer or glTexSubImage). Then though projective texturing you can multi texture your tiles or what ever with this reflection. This is the same method used for doing a vast majority of the reflective water you see every one doing.
Sounds similar to an issue I had when I didn't read the nehe stencil test article properly. Have you specified the number of stencil buffer bits in the pixelformatdescriptor of your window setup code?
taken from the NeHe article:
taken from the NeHe article:
static PIXELFORMATDESCRIPTOR pfd= // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format bits, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 16, // 16Bit Z-Buffer (Depth Buffer) 1, // Use Stencil Buffer ( * Important * ) 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored};This topic is closed to new replies.
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