OpenGL - Revision history

Levidsmith: /* Change BMP to PNG */

2010-05-07T09:00:45Z

Change BMP to PNG

← Older revision		Revision as of 09:00, 7 May 2010
Line 106:		Line 106:

	Another interesting note I found was that all textures MUST be a power of 2 (2, 4, 8, 16, 32, 64, 128, 256, ...) in order to work with OpenGL.		Another interesting note I found was that all textures MUST be a power of 2 (2, 4, 8, 16, 32, 64, 128, 256, ...) in order to work with OpenGL.

			After testing on two Windows Vista machines, I've found that the "texture size must be a power of 2" is HARDWARE dependent. On my desktop system, it will handles texture not a power of 2, but my laptop (running the SAME operating system) will only display those images that are a power of 2 (everything else is black).


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	}		}
	}		}


	== Adding Other Objects ==		== Adding Other Objects ==

2010-02-17T05:22:22Z

Modularizing Code

@@ Line 314: / Line 314: @@
        glVertex3f( x, y + h, 0 );
      glEnd();
+   }

2010-02-17T05:12:39Z

Modularizing Code

← Older revision		Revision as of 05:12, 17 February 2010
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	[[File:Opengl tux08.jpg\|400px]]		[[File:Opengl tux08.jpg\|400px]]


			Wrote a blit texture method to replace all the repeated OpenGL glVertex calls.

			I could have had all the vertices start at (0, 0) and use glTranslate to (x, y). Not sure which way is better, but I know that to rotate an object, the pivot point is always at (0, 0)

			void blitTexture(GLuint img, int x, int y, int w, int h) {
			glLoadIdentity();
			glBindTexture( GL_TEXTURE_2D, img );
			glBegin( GL_QUADS );
			glTexCoord2i( 0, 0 );
			glVertex3f( x, y, 0 );
			glTexCoord2i( 1, 0 );
			glVertex3f( x + w, y, 0 );
			glTexCoord2i( 1, 1 );
			glVertex3f( x + w, y + h, 0 );
			glTexCoord2i( 0, 1 );
			glVertex3f( x, y + h, 0 );
			glEnd();
			}

2010-02-17T02:47:02Z

Modularizing Code

← Older revision		Revision as of 02:47, 17 February 2010
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	I pulled all of that code out into its own function, so now I just simply call loadPNGTexture("filename.png") to load the texture. The function had to be written specific for PNGs, since the RGB/BGR format issue with BMPs.		I pulled all of that code out into its own function, so now I just simply call loadPNGTexture("filename.png") to load the texture. The function had to be written specific for PNGs, since the RGB/BGR format issue with BMPs.

	When I tried using my new method, the entire program ~~crash~~. I found that the reason was because I converted the background from a BMP to a PNG, but I didn't add a transparent layer. Apparently it is REALLY important to make sure you have a transparent layer if you specify RGBA as a parameter to glTexImage2D.		When I tried using my new method, the entire program crashed. I found that the reason was because I converted the background from a BMP to a PNG, but I didn't add a transparent layer. Apparently it is REALLY important to make sure you have a transparent layer if you specify RGBA as a parameter to glTexImage2D.

	GLuint loadPNGTexture(char *strFile) {		GLuint loadPNGTexture(char *strFile) {

2010-02-17T02:46:33Z

Modularizing Code

← Older revision		Revision as of 02:46, 17 February 2010
Line 273:		Line 273:

	I pulled all of that code out into its own function, so now I just simply call loadPNGTexture("filename.png") to load the texture. The function had to be written specific for PNGs, since the RGB/BGR format issue with BMPs.		I pulled all of that code out into its own function, so now I just simply call loadPNGTexture("filename.png") to load the texture. The function had to be written specific for PNGs, since the RGB/BGR format issue with BMPs.

			When I tried using my new method, the entire program crash. I found that the reason was because I converted the background from a BMP to a PNG, but I didn't add a transparent layer. Apparently it is REALLY important to make sure you have a transparent layer if you specify RGBA as a parameter to glTexImage2D.

	GLuint loadPNGTexture(char *strFile) {		GLuint loadPNGTexture(char *strFile) {

2010-02-17T02:44:06Z

Adding Other Objects

← Older revision		Revision as of 02:44, 17 February 2010
Line 266:		Line 266:
	Now I have three OpenGL textures.		Now I have three OpenGL textures.

	[[File:Opengl ~~tux08~~.jpg\|400px]]		[[File:Opengl tux09.jpg\|400px]]




	== Modularizing Code ==		== Modularizing Code ==

2010-02-17T02:41:48Z

← Older revision		Revision as of 02:41, 17 February 2010
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	}		}
	}		}


			== Adding Other Objects ==

			I added a snowman that simply moves in a horizontal motion and bounces off the window border.

			Now I have three OpenGL textures.

			[[File:Opengl tux08.jpg\|400px]]




			== Modularizing Code ==

			With the three textures, I had texture initialization code that was repeated three times.

			I pulled all of that code out into its own function, so now I just simply call loadPNGTexture("filename.png") to load the texture. The function had to be written specific for PNGs, since the RGB/BGR format issue with BMPs.

			GLuint loadPNGTexture(char *strFile) {
			SDL_Surface *surface;
			GLuint giTexture;
			if ( (surface = IMG_Load(strFile)) ) {
			glGenTextures( 1, &giTexture );
			glBindTexture( GL_TEXTURE_2D, giTexture );
			glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
			glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
			glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, surface->w, surface->h, 0,
			GL_RGBA, GL_UNSIGNED_BYTE, surface->pixels );
			}
			if ( surface ) {
			SDL_FreeSurface( surface );
			}
			return giTexture;
			}


			[[File:Opengl tux08.jpg\|400px]]

2010-02-14T05:51:47Z

2010-02-14T05:50:06Z

Change BMP to PNG

2010-02-14T05:38:59Z

Change BMP to PNG

← Older revision		Revision as of 05:38, 14 February 2010
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	Got the transparent PNG image to display correctly. I changed the "format" parameter in the glTeximage2D (noted above) to "GL_RBGA". However, the transparent pixels show up as white instead of the background color.		Got the transparent PNG image to display correctly. I changed the "format" parameter in the glTeximage2D (noted above) to "GL_RBGA". However, the transparent pixels show up as white instead of the background color.

	[[File:Opengl ~~tux05~~.jpg\|400px]]		[[File:Opengl tux06.jpg\|400px]]

			The image now displays correctly with transparency! I had to change the "internalformat" parameter for glTeximage2D from "3" to "GL_RBGA".

			[[File:Opengl tux07.jpg\|400px]]

			Now I just need to write a standard method for generating textures, and I think I will be ready to integrate the code into the main game code.