texture-mapping

I started to play with a OpenGL ES 1.0 and I run into some (beginners) problem: I tried to map a square texture to the cube described by triangles. // Turn necessary features on glEnable(GL_TEXTURE_2D); glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_SRC_COLOR); glEnable(GL_CULL_FACE); //glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Bind the number of textures we need, in this case one. glGenTextures(1, &texture[0]); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);

i use D3DXCreateSphere method to create sphere mesh. and i want to apply an earth texture on it. i calculate the texture coordinate in pixel shader with following code: sampler ShadeSampler = sampler_state { Texture = (ShadeTex); AddressU = Mirror; AddressV = Mirror; MinFilter = LINEAR; MagFilter = LINEAR; MipFilter = LINEAR; }; PS_OUTPUT PSMain(VS_OUTPUT input){ PS_OUTPUT output = (PS_OUTPUT)0; vector uv; uv.x = 0.5 + atan2(input.normal.z, input.normal.x) / piMul2; uv.y = 0.5f - asin(input.normal.y) / pi; vector b = tex2D(ShadeSampler, uv.xy); output.diffuse = b * input.diffuse; return output

Alright, so I started looking up tutorials on openGL for the sake of making a minecraft mod. I still don't know too much about it because I figured that I really shouldn't have to when it comes to making the small modification that I want, but this is giving me such a headache. All I want to do is be able to properly map a texture to an irregular concave quad. Like this: I went into openGL to figure out how to do this before I tried running code in the game. I've read that I need to do a perspective-correct transformation, and I've gotten it to work for trapezoids, but for the life of me I can

I am working on an OpenGL ES fluid simulation which uses texture maps to hold grid values. I need to iterate thru the grid that mimics the following loop: for (int r = 0; r < 128; r++) for (int c = 0; c < 128; c++) process grid element at (c,r) To iterate through the grid I am simply filling a quadrilateral which causes my fragment program to be invoked for each fragment. The texture coordinates (0,0), (1,0), (0,1), (1,1) are associated with the vertices (-1,-1), (+1,-1), (-1,+1), (+1,+1) and I render the quad (as a triangle strip) into a 128x128 texture map attached to a FBO as follows:

I have tried to add a fairly simple extension on top of Android's example OpenGL 2.0 project in order to add texturing to basic shapes. This seems pretty straightforward, but on certain devices (Samsung Nexus S, LG Optimus 3D, Samsung Galaxy S) the texture just does not render. This is actually a problem that I am having on a much larger project, but I was able to reproduce the issue with the simple project below in the hope that someone here has an idea of where my code presents issues, or how to specifically architect GL textures for these devices (maybe there are issues with the devices).

I want to use a 1d texture (color ramp) to texture a simple triangle. My fragment shader looks like this: #version 420 uniform sampler1D colorRamp; in float height; out vec4 FragColor; void main() { FragColor = texture(colorRamp, height).rgba; } My vertex shader looks like this: #version 420 layout(location = 0) in vec3 position; out float height; void main() { height = (position.y + 0.75f) / (2 * 0.75f); gl_Position = vec4( position, 1.0); } When drawing the triangle I proceed this way (I removed error checking form code for better readability): glUseProgram(program_); GLuint samplerLocation

I would like to know a theoretical reasoning why is this even possible: how translation of the geometry is related to the texture mapping. I can only notice this effect when making a sub-pixel translation, texture looks fine if translated by entire pixel(s). I am using orthographic projection, GL_CLAMP_TO_EDGE , GL_NEAREST , fragment shader is highp . Texture coordinates is a subregion of the atlas, but I can see the distortion even if the entire atlas is mapped. Using OpenGL ES (Android and iOS), but please before retagging could anyone explain that this is not an issue in OpenGL. Things I've