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January 04 2011
GLGraphics | Download GLGraphics software for free at SourceForge.net
GLGraphics is a library for the Processing programming language that offers a number of classes to simplify the handling of OpenGL textures, GLSL shaders and off-screen rendering inside Processing.August 03 2010
[Moof:Bar]: Implementing iBooks page curling using a conical deformation algorithm
"still relatively new to OpenGL and Objective-C in general" and amazing.[Moof:Bar]: Implementing iBooks page curling using a conical deformation algorithm
"still relatively new to OpenGL and Objective-C in general" and amazing.July 24 2010
http://developer.download.nvidia.com/opengl/specs/GL_ARB_texture_swizzle.txt
Classic OpenGL texture formats conflate texture storage and interpretation, and assume that textures represent color. In modern applications, a significant quantity of textures don't represent color, but rather data like shadow maps, normal maps, page tables, occlusion data, etc.. For the latter class of data, calling the data "RGBA" is just a convenient mapping of what the data is onto the current model, but isn't an accurate reflection of the reality of the data.The existing texture formats provide an almost orthogonal set of data types, sizes, and number of components, but the mappings of this storage into what the shader or fixed-function pipeline fetches is very much non-orthogonal.
This extension provides a mechanism to swizzle the components of a texture before they are applied according to the texture environment in fixed-function or as they are returned to the shader.
http://developer.download.nvidia.com/opengl/specs/GL_ARB_texture_swizzle.txt
Classic OpenGL texture formats conflate texture storage and interpretation, and assume that textures represent color. In modern applications, a significant quantity of textures don't represent color, but rather data like shadow maps, normal maps, page tables, occlusion data, etc.. For the latter class of data, calling the data "RGBA" is just a convenient mapping of what the data is onto the current model, but isn't an accurate reflection of the reality of the data.The existing texture formats provide an almost orthogonal set of data types, sizes, and number of components, but the mappings of this storage into what the shader or fixed-function pipeline fetches is very much non-orthogonal.
This extension provides a mechanism to swizzle the components of a texture before they are applied according to the texture environment in fixed-function or as they are returned to the shader.
July 14 2010
MachWerx » Blog Archive » glBlendFunc()
If you’re doing 3D graphics on the iPhone, you’re mostly dealing with OpenGL. And if you’re doing OpenGL, you’re using glBlendFunc(GLenum source_factor, GLenum destination_factor) to indicate how polygons draw on top of each other. The way it works is it multiplies a source image (what you’re putting on top) by something, multiplies the destination image (the background) by something, and adds the two results together. The glBlendFunc() specifies what those two somethings are.MachWerx » Blog Archive » glBlendFunc()
If you’re doing 3D graphics on the iPhone, you’re mostly dealing with OpenGL. And if you’re doing OpenGL, you’re using glBlendFunc(GLenum source_factor, GLenum destination_factor) to indicate how polygons draw on top of each other. The way it works is it multiplies a source image (what you’re putting on top) by something, multiplies the destination image (the background) by something, and adds the two results together. The glBlendFunc() specifies what those two somethings are.July 12 2010
Bug in GL10.texSubImage2D? - Android Developers | Google Groups
Robert Green writes "You can texImage2D the same textureId as many times as you like."Bug in GL10.texSubImage2D? - Android Developers | Google Groups
Robert Green writes "You can texImage2D the same textureId as many times as you like."July 07 2010
OpenGL Invariance: Texture AA
Using texture mapping for geometry antialiasing is not a new idea. I found descriptions and presentations about it, but no actual code. The basic idea is to replace the original primitive with texture mapped triangles, as illustrated:The texture applied to the triangles is simply an antialiased circle. Slices of the circle are stretched out for the line and triangle cases. To accommodate fractionally variable primitive sizes, we can generate the circle texture at an arbitrary maximum size and generate mipmaps for smaller sizes. Trilinear mipmapping will then approximate a texture for any desired size.
OpenGL Invariance: Texture AA
Using texture mapping for geometry antialiasing is not a new idea. I found descriptions and presentations about it, but no actual code. The basic idea is to replace the original primitive with texture mapped triangles, as illustrated:The texture applied to the triangles is simply an antialiased circle. Slices of the circle are stretched out for the line and triangle cases. To accommodate fractionally variable primitive sizes, we can generate the circle texture at an arbitrary maximum size and generate mipmaps for smaller sizes. Trilinear mipmapping will then approximate a texture for any desired size.
7.5 Antialiasing with Accumulation Buffer
Accumulation buffers can be used to antialias a scene without having to depth sort the primitives before rendering. A supersampling technique is used, where the entire scene is offset by small, subpixel amounts in screen space, and accumulated. The jittering can be accomplished by modifying the transforms used to represent the scene.7.5 Antialiasing with Accumulation Buffer
Accumulation buffers can be used to antialias a scene without having to depth sort the primitives before rendering. A supersampling technique is used, where the entire scene is offset by small, subpixel amounts in screen space, and accumulated. The jittering can be accomplished by modifying the transforms used to represent the scene.July 05 2010
Advanced Texturing DMS 423 - Class 17
Transformations - translation, rotation, and scaling - can be applied to texture coordinates, similar to how they are applied to geometry.The exact same OpenGL function calls are used. The only difference is that the matrix mode is changed to GL_TEXTURE.
glMatrixMode(GL_TEXTURE)
glTranslatef(0.1, 0.05, 0)
glRotatef(30.0, 0, 0, 1)
glMatrixMode(GL_MODELVIEW)
Setting the matrix mode to GL_TEXTURE means that any subsequent transformation calls will be applied to texture coordinates, rather than vertex coordinates.
July 03 2010
Triangle Strip for Grids – A Construction
It wasn’t immediately obvious how to define a grid out of a single triangle strip and so I got out a pen and paper. I kept in mind a neat trick: if in a triangle strip, you need to skip the use of a vertex, a vertex can be introduced twice in a row. That is, if I need triangles (6, 3, 7) and (7, 11, 6) in that order, you can just make your strip with 6, 3, 7, 7, 11, 6. You can think of it as if there are two triangles created (3, 7, 7) and (7, 7, 11), but they have no area and a degenerate case – a line. Furthermore, these lines lie on triangles already defined.June 29 2010
blending.jpg 800×600 pixels
table showing interactions between six different OpenGL blend modes: GL_ZERO, GL_ONE, GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR, GL_SRC_ALPHA, and GL_ONE_MINUS_SRC_ALPHA
table showing interactions between six different OpenGL blend modes: GL_ZERO, GL_ONE, GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR, GL_SRC_ALPHA, and GL_ONE_MINUS_SRC_ALPHA
June 28 2010
CodeSampler.com - Particle System Using Optimized Billboards
"This sample is basically a performance test for particle systems, which allows you to switch between three different methods of creating eye-rotated billboards. For the first method, billboard calculations are done manually and take place totally on the CPU by the application. For the second method, the particle system uses ARB_point_sprite extension to offload the creation of billboards to the GPU. And finally, the third method uses Cg to build billboards on the GPU via a vertex shader." And, a bunny.October 21 2009
October 19 2009
OBJ2OPENGL - Convert OBJ file to OpenGL format
OBJ2OPENGL is a PERL script that reads an OBJ file describing a 3D object, and writes a C include file describing the object in a form suitable for use with Open GL. To see how to use the include file created by this program, refer to the example in the Open GL examples directory. The author wishes to point out that this script was developed for a specific purpose, and was not intended to be able to handle all variations of the OBJ file format.October 18 2009
Forays Into iPhone OpenGL ES | Serg Koren
If you create, build and run the sample template you end up with an iPhone application that spins a multicolored square... Part I - The iPhone OpenGL ES XCode Template Header Dissected
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