glsl

I must have misunderstood something with shaders: I thought that as you can attach multiple shaders to one program, you'd be able to simply attach more than one fragment shader, as an example: A crate texture rendered with a color modulation and refraction. But apparently this is not the case, as you can have only one main function per program. How can I work around the main function limit and allow for any dynamic combination of multiple fragment shaders which are in the same program and called after each other? You can have a set of entry points pre-defined. Suppose you have a limited number

I have been working with OpenGL in iOS, and setting the colors with glColor4f(r,g,b,a) and then drawing my own color on a white UIImageView . I basically have a brush, which is then moved around my user's touch, and then it paints the color onto the canvas. But this color needs to be water paint (like smudged color) Does anyone understand/knows how to get a water color like this app does, and how the background UIImageView has a texture on it? https://itunes.apple.com/us/app/hello-watercolor/id539414526?mt=8 or checkout water paint in this. http://www.fiftythree.com/paper I created a bounty on

I can't seem to find a clear answer on this, despite hours of googling. Can someone just tell me what's going on? I get errors saying things like, "version 140 is not supported." Is this my device (Kindle Fire) or GL ES 2.0? Do I need to add libraries or anything? you actually don't have to add any libraries, 140 is far too new for Kindle Fire. Either remove the version specification or decrement it until the shader compiles. You may need to fix some other errors in the shader as the individual versions of the language do have some differences. You can also query GL_SHADING_LANGUAGE_VERSION

I want actual world space distance, and I get the feeling from experimentation that (gl_FragCoord.z / gl_FragCoord.w) is the depth in world space? But I'm not too sure. EDIT I've just found where I had originally located this snippet of code . Apparently it is the actual depth from the camera? This was asked (by the same person) and answered elsewhere . I'm paraphrasing and embellishing the answer here: As stated in section 15.2.2 of the OpenGL 4.3 core profile specification (PDF) , gl_FragCoord.w is 1 / clip.w , where clip.w is the W component of the clip-space position (ie: what you wrote to

What is the convention OpenGL follows for cubemaps? I followed this convention (found on a website) and used the correspondent GLenum to specify the 6 faces GL_TEXTURE_CUBE_MAP_POSITIVE_X_EXT but I always get wrong Y, so I have to invert Positive Y with Negative Y face. Why? ________ | | | pos y | | | _______|________|_________________ | | | | | | neg x | pos z | pos x | neg z | | | | | | |_______|________|________|________| | | | | | neg y | |________| but I always get wrong Y, so I have to invert Positive Y with Negative Y face. Why? Ah, yes, this is one of the most odd things about Cube

I am trying to do some image processing on the GPU, e.g. median, blur, brightness, etc. The general idea is to do something like this framework from GPU Gems 1. I am able to write the GLSL fragment shader for processing the pixels as I've been trying out different things in an effect designer app. I am not sure however how I should do the other part of the task. That is, I'd like to be working on the image in image coords and then outputting the result to a texture. I am aware of the gl_FragCoords variable. As far as I understand it it goes like that: I need to set up a view (an orthographic

It seems this should be easy but I'm having a lot of difficulty using part of a texture with a point sprite. I have googled around extensively and turned up various answers but none of these deal with the specific issue I'm having. What I've learned so far: Basics of point sprite drawing How to deal with point sprites rendering as solid squares How to alter orientation of a point sprite How to use multiple textures with a point sprite , getting closer here.. That point sprites + sprite sheets has been done before, but is only possible in OpenGL ES 2.0 (not 1.0) Here is a diagram of what I'm

I want to adjust the colors depending on which xyz position they are in the world. I tried this in my fragment shader: varying vec4 verpos; void main(){ vec4 c; c.x = verpos.x; c.y = verpos.y; c.z = verpos.z; c.w = 1.0; gl_FragColor = c; } but it seems that the colors change depending on my camera angle/position, how do i make the coords independent from my camera position/angle? Heres my vertex shader: varying vec4 verpos; void main(){ gl_Position = ftransform(); verpos = gl_ModelViewMatrix*gl_Vertex; } Edit2: changed title, so i want world coords, not screen coords! Edit3: added my full code