OpenGL is a graphics standard and API which targets the desktop and workstation markets. It is designed to be easy to accelerate with dedicated computer hardware, and hence most implementations give greatly improved performance over traditional software rendering. Currently, OpenGL is used for ...

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1answer
280 views

Distorted LookAt When Looking Up or Down?

I have a weird problem and I have no idea what's going on with it. Recently started doing some OpenGL programming, going pretty well, hit some rough spots but worked my way through them and otherwise ...
1
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0answers
415 views

opengl volumetric billboard implementation: general idea + geometry shader [closed]

A while ago I decided to implement the volumetric billboards technique in my university project (C++ & OpenGL 4.3). I passed the subject but failed to implement the mentioned technique. I'd like ...
0
votes
1answer
80 views

How do I follow this glsl1.2 + lights + shadows tutorial?

I am following this great tutorial but I have many questions. Let's see if I understand the basic idea. 1. I must create the same number of FBOs that lights (maximum 8). 2. I must create the same ...
4
votes
2answers
365 views

GLSL: sampler2D fallback to constant color?

So I have the following situation: I'm sharing a blinn shader accross many meshes. Some meshes have specular & normal maps, others do not. I'd like to, without making the shader code too ...
1
vote
2answers
410 views

How to reduce/remove graphical artifacts?

Question I'm working on a side-scrolling game that has a 2D grid for rendering to the screen. I'm using OpenGL, and I've optimized my game so that nothing invisible is attempted to be drawn. As of ...
0
votes
1answer
359 views

making a cone roof look hollow

How can I make a cone roof look hollow when viewed from underneath? I am trying to create a cone shaped roof, but the cone does not look much like a roof, the edges of the roof seem to blend with ...
2
votes
2answers
353 views

How can I determine the pixels covered by a transformed triangle (without drawing it)?

I have three points that form a triangle in a 3D scene. I want to apply an arbitrary rotation/translation transformation to this polygon and later check in which pixels of an image they would be ...
5
votes
1answer
315 views

How can I implement real-time mutual object reflection?

So, given a scene like this (cubemap skybox with "real" spheres) Everything looks great, except for the fact that the spheres don't reflect each other. What's a good way to go about this? The ...
5
votes
2answers
689 views

Are display lists faster than VBOs?

I'm making a voxel rendering engine. My "chunks" are 32 * 32 * 256 blocks and I can render a 16 * 16 square of them (which corresponds to Minecraft's maximal render distance). I'm using VBOs holding ...
2
votes
2answers
743 views

3D position to UV coordinates in fragment shader

I am interested in converting an arbitrary 3D position computed at run time in the fragment shader to its corresponding UV coordinates. Notice that the 3D position I am interested in is NOT a 3D ...
3
votes
2answers
310 views

Is there any reason why there isn't a cross-platform implementation of DirectX?

Similar to how Mono can compile C# to various platforms, why isn't there an API that conforms to DirectX's specifications but can produce binaries for all platforms? I understand that there is OpenGL ...
27
votes
5answers
4k views

Why do we use 4x4 matrices to transform things in 3D?

To translate a vector by 10 unit in the X direction, why do we have to use a matrix? We can just add 10 to the mat[0][0], and we got the same result too.
1
vote
1answer
114 views

In glsl, how do indices work?

I have made a vertex shader and fragment shader and kind of know how they work, and I know that you specify what index you want your vertices to be in inside the shader program. So if the vertex was ...
0
votes
1answer
360 views

(LWJGL) Pixel Unpack Buffer Object is Disabled? (glTextImage2D)

I am trying to create a render target for my game so that I can re-render at a different screen size. But I am receiving the following error: Exception in thread "main" ...
1
vote
1answer
214 views

glOrtho setting view [closed]

I am duplicating this thread from stackoverflow, please remove it if that is not allowed. I'm completely new in OpenGL. I have this problem: I have quite a complicated scene, and I am looking at it ...
1
vote
1answer
2k views

Anti Aliasing: How to implement supersampling in OpenGL?

I'm learning OpenGL by working on a small Oculus Rift project, which implies, anti aliasing is everything :). Since the application of the barrel distortion shader requires rendering to a framebuffer ...
2
votes
0answers
429 views

OpenGL drawing 500k triangles [closed]

I want to render big, izometric 2d map (using ortho projection). I am using OpenTK and aiming for OpenGL 3.3. Perfect option would be to draw 512x512 map of tiles, which is 262144 blocks -> 524288 ...
7
votes
3answers
867 views

Terrain & Multi-Texturing

I'm using OpenGL (Version 4.4) (and C++ if that matters). I've created a terrain renderer, the terrain is stored as a 3D scalar field (isosurface/voxels). It uses a slightly modified version of ...
3
votes
2answers
440 views

Blending semi-transparent images while not stacking their alphas

In libgdx/OpenGL ES I want to render multiple semitransparent textures while keeping the alpha still semi transparent. For example If I render a 0.5 alpha circle on top of another 0.5 alpha circle, ...
4
votes
1answer
2k views

How can I forward GLFW's keyboard input to another object?

I'm having trouble trying to execute keyboard events in a another class with GLFW3. The problem I'm having is that GLFW3 uses a static function for input as shown: static UI u; ... ... static void ...
0
votes
1answer
1k views

OpenGL Reconstructing Position from Depth

I know this has been asked a lot of time before but none of those answers fixed my problem. I try to implement deferred shading and to do so I need to reconstruct the world space position from the ...
0
votes
1answer
1k views

Why do I get “function not supported” exceptions for OpenGL 3.2 functions using LWJGL?

I am currently having an issue trying to initialize a frame buffer using LWJGL. When I try to call GL32.glFramebufferTexture(int, int, int, int) it throws a "Function is not supported" error. I have ...
1
vote
1answer
683 views

GLSL - std140 uniform block - fields(vec, float, mat4) always 0.0

Ok, First of all, if just use uniforms everthing works like it should. Switching to uniform blocks nothing goes, as all values look like 0.0. I tested this with various if-then-else stuff within the ...
0
votes
1answer
207 views

Events management using SDL 2.0

I wrote a simple SDL program using SDL 2.0. I have a little problem when I want to check the mouse wheel events. Actually, in the version 2.0 the flags SDL_BUTTON_WHEELDOWN and SDL_BUTTON_WHEELUP no ...
0
votes
1answer
355 views

(LWJGL) Resize window content [closed]

I am having a little issue with my game trying to get the screen to draw a ton larger. I am going for a retro type of feel for my game and I believe that this would help with that. I am basically ...
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0answers
212 views

How can I draw a part of a texture in slick2d?

I know the method for drawing a region of a texture in slick2d: image.draw(x, y, srcX, srcY, srcX2, srcY2); But I have no idea how the texture coordinates work. To draw a region of x:16, y:16, ...
2
votes
1answer
827 views

glDeleteTextures - release data, but keep the texture ID?

In OpenGL, is it possible to release texture data, but keep the same texture id? I want to unload textures when they aren't needed, but load them again later when they are. There are a lot of objects ...
2
votes
1answer
144 views

Does Direct3D have hardware-dependant extensions like OpenGL?

I am not familiar with Direct3D and I want to know if it has hardware and vendor dependant functions like the extensions in OpenGL? A program written by a friend fails on certain computers while it ...
6
votes
1answer
1k views

OpenGL ES object rotation around z axis

I have an object on my screen which is presented rotated and panned, But i have 2 problems regarding the z axis rotations. It's a bit tricky to explain so i uploaded 2 videos to describe each problem. ...
3
votes
2answers
220 views

Efficient way to output/display debugging data in a window

I'm writing a program in Visual Studio, C++ with OpenGL and for the first time, I think it will be beneficial to see some live data on top of my display/render window. To give some scope, I'm ...
1
vote
1answer
209 views

GLSL associating multiple uniform samplerBuffers

At the moment I'm not sure how my VBO and TBO associate with a specific uniform samplerBuffer in my shader, I have not linked them using the location or the vbo/tbo together. It seems to still work ...
2
votes
0answers
1k views

Normal mapping does not work correctly using GLSL and OpenGL [closed]

Hello I wrote a simple OpenGl program using GLSL to render a simple uv mapped plane using the normal mapping technics. Here's the display with a simple phong shading (without normal mapping) : Now ...
1
vote
1answer
163 views

Given face normal and vertices of a triangle, how to find the acyclic order of vertices?

I'm in the process of constructing a custom 3D triangle mesh. I found the vertices of the triangle in the 3D space and it's face normal. How do I find the acyclic order of vertices? If I draw the ...
1
vote
1answer
229 views

How do I flip upside down fonts in FTGL [closed]

I just use FTGL to use it in my app. I want to use the version FTBufferFont to render font but it renders in the wrong way. The font(texture?buffer?) is flipped in the wrong axis. I want to use ...
1
vote
1answer
191 views

Most common format & good practice for 3D models for a placeholder in a PC game [closed]

I'm soon starting programming my first 3D game in OpenGL, C++, for PC. It's going to be a top-down space-based game. Early on I want to create basic placeholder 3D models for my objects, and then in ...
0
votes
3answers
1k views

OpenGL - How to draw a transition of two textures on one quad?

I know when drawing a rectangle, if we select red and draw two vertices, and then select yellow and draw the other two vertices, the entire rectangle will show a nice transition of color between those ...
0
votes
0answers
46 views

OpenGL - How to use depth checking and alpha blending at the same time? [duplicate]

Suppose I have a semi-transparent object (let's call this "bubble"), a solid object (let's call this "wall"), and the bubble is closer to the camera compared to the wall behind it. If I draw the ...
1
vote
1answer
141 views

OpenGL Fragment Shader Interpolation Vs Inverse Calculation

I have found openGL fragment shader tutorials on the web, some that use use inverse calculations to revert the fragment coordinate back to the world space and others that interpolate the position. ...
1
vote
1answer
1k views

How Extract Frustum Planes from Clip Coordinates?

I'm having some problems with my Frustum Culling and I want to debug it, so I'm trying to render it's planes, to see exatly the Frustum. But I'm using the Clip Coordinates to do the culling (like ...
0
votes
0answers
462 views

Why does Assimp appear to be loading vertices in the incorrect order in this code?

I'm getting a weird bug in my code that is reading in the vertices from an .obj file. The .obj file is just a cube, hence there are eight vertices. When I print out the vector it seems to work ...
3
votes
1answer
559 views

First encounter with dynamic lighting [closed]

I have a game idea with lots of pretty lights (literally) in mind that I would really love to implement, but I have essentially zero experience with shadow mapping, deferred rendering, the lot of it. ...
1
vote
0answers
348 views

Rendering portals using stencil buffer

Due to this question I have changed the method of rendering portals. Before I was using FBO and rendering to a texture, but somehow I failed. Now I switched to a stencil buffer method. My problem is ...
3
votes
2answers
2k views

When would you use an octree in a voxel Engine?

I've been reading about Octrees, and I understand how they work (or at least I think I do). However, I can't figure out why you would use octrees instead of a simple multidimensional array. In my ...
2
votes
2answers
745 views

Why is GL_TEXTURE_MAX_ANISOTROPY_EXT undefined?

So I'm writing my texture class in my opengl game, I get to the part where I would normally set GL_TEXTURE_MAX_ANISOTROPY_EXT, and I'm shocked to discover that it's undefined! This exact same ...
6
votes
1answer
353 views

With what projection matrix should I render a portal to a texture?

I'm using OpenGL. I have problem with my engine's portal implementation. To create the first portal I do: create a virtual camera with the position of the second portal and the correct orientation ...
1
vote
2answers
663 views

Decoupling rendering pipeline (for UI responsiveness): Multithreading and multiple contexts?

Warning! Wall of text (see <TL;DR> paragraphs below for short version) I have been noticing something in quite many games (most recently in cutting-edge RTS games such as Uber Entertainment's ...
2
votes
1answer
219 views

Mouse Speed in GLUT and OpenGL?

I would like to simulate a point that moves in 2D. The input should be the speed of the mouse, so the new position will be computed as following new_position = old_position + ...
0
votes
1answer
361 views

Build unity like Transform class [closed]

I am building a Unity-like Transform class. This is my header file: #include "Common.h" struct Transform { public: Transform(); void Translate(float x, float y, float z); ...
-2
votes
1answer
150 views

Why OpenGL X and Z axis got inverted sometimes?

I'm having some troubles with my game code. I'm developing a Voxel Engine and everything is fine, but sometimes (like 30% of times) when I build and run my project, the X and Z axis got inverted (I ...
3
votes
1answer
199 views

How can I GL_SELECT from a gluPerspective-transformed scene?

I'm using JOGL to access OpenGL-methods on an old OpenGL version, because of school. I have written a method which is called before any objects are drawn. This method shows which object is picked. ...