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Changes between Version 9 and Version 10 of people/boenzlip/interesstingStuff


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Timestamp:
Jan 28, 2006, 4:34:45 PM (15 years ago)
Author:
patrick
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  • people/boenzlip/interesstingStuff

    v9 v10  
    1515
    1616
    17 == Explosions, Particle Rendering - from NeHe ==
    18 source = http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=30 [[br]]
    19 Every time a collision takes place an explosion is triggered at the collision point. A nice way to model explosions is to alpha blend two polygons which are perpendicular to each other and have as the center the point of interest (here intersection point). The polygons are scaled and disappear over time. The disappearing is done by changing the alpha values of the vertices from 1 to 0, over time. Because a lot of alpha blended polygons can cause problems and overlap each other (as it is stated in the Red Book in the chapter about transparency and blending) because of the Z buffer, we borrow a technique used in particle rendering. To be correct we had to sort the polygons from back to front according to their eye point distance, but disabling the Depth buffer writes (not reads) also does the trick (this is also documented in the red book). Notice that we limit our number of explosions to maximum 20 per frame, if additional explosions occur and the buffer is full, the explosion is discarded. The source which updates and renders the explosions is:
    20 {{{
    21 
    22 / Render / Blend Explosions
    23 glEnable(GL_BLEND);                                                     // Enable Blending
    24 glDepthMask(GL_FALSE);                                                  // Disable Depth Buffer Writes
    25 glBindTexture(GL_TEXTURE_2D, texture[1]);                               // Upload Texture
    26 for(i=0; i<20; i++)                                                     // Update And Render Explosions
    27 {
    28         if(ExplosionArray[i]._Alpha>=0)
    29         {
    30                 glPushMatrix();
    31                 ExplosionArray[i]._Alpha-=0.01f;                        // Update Alpha
    32                 ExplosionArray[i]._Scale+=0.03f;                        // Update Scale
    33                 // Assign Vertices Colour Yellow With Alpha
    34                 // Colour Tracks Ambient And Diffuse
    35                 glColor4f(1,1,0,ExplosionArray[i]._Alpha);              // Scale
    36                 glScalef(ExplosionArray[i]._Scale,ExplosionArray[i]._Scale,ExplosionArray[i]._Scale);
    37                 // Translate Into Position Taking Into Account The Offset Caused By The Scale
    38                 glTranslatef((float)ExplosionArray[i]._Position.X()/ExplosionArray[i]._Scale,
    39                         (float)ExplosionArray[i]._Position.Y()/ExplosionArray[i]._Scale,
    40                         (float)ExplosionArray[i]._Position.Z()/ExplosionArray[i]._Scale);
    41                 glCallList(dlist);                                      // Call Display List
    42                 glPopMatrix();
    43         }
    44 }
    45 
    46 }}}
    47 
    4817= Collision Detection Systems/ Algorithms =
    49 Links: http://www.cs.unc.edu/~dm/collision.html
     18Links:
     19http://www.cs.unc.edu/~dm/collision.html
     20http://www.harveycartel.org/metanet/tutorials/tutorialA.html - this one is realy good
    5021= Libraries  =
    5122 * [http://www.ams.sunysb.edu/~jklosow/quickcd/QCD_kdops.html Discrete Orientation Polytopes (k-DOPs)]