GLSL custom interpolation filter

Posted by Cyan on Game Development See other posts from Game Development or by Cyan
Published on 2012-11-15T14:54:27Z Indexed on 2012/11/15 17:24 UTC
Read the original article Hit count: 196

Filed under:

textures

|

glsl

|

interpolation

I'm currently building a fragment shader which is using several textures to render the final pixel color.

The textures are not really textures, they are in fact "input data" to be used in the formula to generate the final color.

The problem I've got is that the texture are getting bi-linear-filtered, and therefore the input data as well. This results in many unwanted side-effects, especially when final rendered texture is "zoomed" compared to original resolution.

Removing the side effect is a complex task, and only result in "average" rendering. I was thinking : well, all my problems seems to come from the "default" bi-linear filtering on these input data. I can't move to GL_NEAREST either, since it would create "blocky" rendering. So i guess the better way to proceed is to be fully in charge of the interpolation.

For this to work, i would need the input data at their "natural" resolution (so that means 4 samples), and a relative position between the sampled points. Is that possible, and if yes, how ?

[EDIT] Since i started this question, i found this internet entry, which seems to (mostly) answer my needs. http://www.gamerendering.com/2008/10/05/bilinear-interpolation/

One aspect of the solution worry me though : the dimensions of the texture must be provided in an argument. It seems there is no way to "find this information transparently". Adding an argument into the rendering pipeline is unwelcomed though, since it's not under my responsibility, and translates into adding complexity for others.

© Game Development or respective owner

Related posts about textures

Textures on top of other textures when using VBOs

as seen on Game Development - Search for 'Game Development'
I'm currently making a cube style game. With chunks being drawn with VBOs. I'd like to know if there is a way to create an overlay texture on top of the existing texture without the need to rebuild the VBO. This is required to show activity in a cube (think of Minecraft when destroying a block and… >>> More
Texture switching with a entity system

as seen on Game Development - Search for 'Game Development'
I'm using thinking of using an entity system in my game. So far I've been using Artemis with success. However, I have a question about texture switching. I read that switching textures too often is bad. So I load all the textures when the game loads like so: import org.newdawn.slick.opengl.TextureLoader; … >>> More
SFML: Generate a background image

as seen on Game Development - Search for 'Game Development'
I want to generate a background, which is used in the game, on every instance of the game based on certain conditions. To do so, I'm using a sf::RenderTexture and a sf::Texture like this: sf::RenderTexture image; std::vector<sf::Texture> textures; sf::Texture texture; // instantiating the vector… >>> More
Unity: how to apply programmatical changes to the Terrain SplatPrototype?

as seen on Game Development - Search for 'Game Development'
I have a script to which I add a Terrain object (I drag and drop the terrain in the public Terrain field). The Terrain is already setup in Unity to have 2 PaintTextures: 1 is a Square (set up with a tile size so that it forms a checkered pattern) and the 2nd one is a grass image: Also the Target… >>> More
SDL2 sprite batching and texture atlases

as seen on Game Development - Search for 'Game Development'
I have been programming a 2D game in C++, using the SDL2 graphics API for rendering. My game concept currently features effects that could result in even tens of thousands of sprites being drawn simultaneously to the screen. I'd like to know what can be done for increasing rendering efficiency if… >>> More

Related posts about glsl

How to debug a GLSL shader ?

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to debug a GLSL program but I don't know how to output intermediate result. Is it possible to make some debug traces (like with printf) with GLSL ? >>> More
How to update a uniform variable in GLSL

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi All, I am trying to get update the eye position in my shader from my appliaction but I keep getting error 1281 when I attempt this. I have no problems after the initialization just when i subsequently try to update the values. Here is my code: void GraphicsObject::SendShadersDDS(char vertFile… >>> More
GLSL check if fragment is on geometry

as seen on Stack Overflow - Search for 'Stack Overflow'
I am currently writing the positions of my geometry to the RGB channels of gl_FragColor and I would like to write 1.0 to the alpha channel if the fragment is part of geometry, and 0.0 if its empty. Is there a simple way to tell if a fragment is geometry or not? Maybe through gl_FragCoord.z? thanks >>> More
Implementing your own depth buffer with GLSL

as seen on Stack Overflow - Search for 'Stack Overflow'
I need a datastructure of the same size as the normal depth buffer and I need to be able to read from and write to it in a shader. Is this possible, and what does this datastructure look like? >>> More
Passing multiple Vertex Attributes in GLSL 130

as seen on Game Development - Search for 'Game Development'
(note this question is closely related to this one however I didn't fully understand the accepted answer) To support videocards in laptops I have to rewrite my GLSL 330 shaders to GLSL 130. I'm trying to do this but somehow I don't get vertex attributes to work properly. My 330 shaders look like… >>> More