glsl

I need to pass from RGB color space to HSV .. I searched in internet and found two different implementations, but those give me different results: A: precision mediump float; vec3 rgb2hsv(float r, float g, float b) { float h = 0.0; float s = 0.0; float v = 0.0; float min = min( min(r, g), b ); float max = max( max(r, g), b ); v = max; // v float delta = max - min; if( max != 0.0 ) s = delta / max; // s else { // r = g = b = 0 // s = 0, v is undefined s = 0.0; h = -1.0; return vec3(h, s, v); } if( r == max ) h = ( g - b ) / delta; // between yellow & magenta else if( g == max ) h = 2.0 + ( b -

I've been learning OpenGL for the past couple of weeks and I've run into some trouble implementing a Phong shader. It appears to do no interpolation between vertexes despite my use of the smooth qualifier. Am I missing something here? To give credit where credit is due, the code for the vertex and fragment shaders cribs heavily from the OpenGL SuperBible Fifth Edition. I would highly recommend this book! Vertex Shader: #version 330 in vec4 vVertex; in vec3 vNormal; uniform mat4 mvpMatrix; // mvp = ModelViewProjection uniform mat4 mvMatrix; // mv = ModelView uniform mat3 normalMatrix; uniform

I am trying to study shadow mapping in WebGL. I see same piece of shader code copied in various libraries and examples that achieve this. However nowhere did I find the explanation of how it works. The idea is to save a depth value (a single float) into the color buffer (vec4). There is a pack function that saves float to vec4 and unpack function that retrieves the float from vec4. vec4 pack_depth(const in float depth) { const vec4 bit_shift = vec4(256.0*256.0*256.0, 256.0*256.0, 256.0, 1.0); const vec4 bit_mask = vec4(0.0, 1.0/256.0, 1.0/256.0, 1.0/256.0); vec4 res = fract(depth * bit_shift);

My problem is getting more than one texture accessible in a GLSL shader. Here's what I'm doing: Shader: uniform sampler2D sampler0; uniform sampler2D sampler1; uniform float blend; void main( void ) { vec2 coords = gl_TexCoord[0]; vec4 col = texture2D(sampler0, coords); vec4 col2 = texture2D(sampler1, coords); if (blend > 0.5){ gl_FragColor = col; } else { gl_FragColor = col2; } }; So, I simply choose between the two color values based on a uniform variable. Simple enough (this is a test), but instead of the expected behavior, I get all black when blend <= 0.5 . OpenGL code: m_sampler0location

I have a shader that ideally needs 28 bits of mantissa, though I can use less and degrade performance. How can I determine what the precision of 'highp' is in OpenGL ES? It's probably an FP24, with 16bits mantissa, but I cannot figure out for sure or how to ask OpenGL. Any ideas? You want GetShaderPrecisionFormat to query the range and precision of of shader types int range[2], precision; glGetShaderPrecisionFormat(GL_FRAGMENT_SHADER, GL_HIGH_FLOAT, range, &precision); will give you the range and precision of highp float. From the OpenGL ES Shading Language reference : highp - 16-bit, floating

Elsewhere on StackOverflow a question was asked regarding a depthbuffer histogram - Create depth buffer histogram texture with GLSL . I am writing an iOS image-processing app and am intrigued by this question but unclear on the answer provided. So, is it possible to create an image histogram using the GPU via GLSL? Yes, it is. It's not clearly the best approach, but it's indeed the best one available in iOS, since OpenCL is not supported. You'll lose elegance, and your code will probably not as straightforward, but almost all OpenCL features can be achieved with shaders. If it helps, DirectX11

I have some simple polygons (fewer than 20 vertices) rendering flat on a simple xy plane, using GL_TRIANGLES and a flat color, a 2d simulation. I would like to add a border of variable thickness and a different color to these polygons. I have something implemented using the same vertices and glLineWidth/GL_LINE_LOOP, which works, but is another rendering pass and repeats all the vertex transforms. I think I should be able to do this in the fragment shader using gl_FragCoord and the vertex data and/or texture coordinates, but I'm not sure, and my naive attempts have been obviously incorrect. I