Sign in to follow this  
Thrump

OpenGL Lighting (complete darkness not working)

Recommended Posts

I'm having trouble getting rid of all lighting in a scene (ie, I want the screen completely black). There always seems to be a very low ambient light in the scene. I first tried setting the ambient and diffuse settings to black, that didn't work. I then disabled all 8 light sources (0-7) but still have the same problem. Setting material properties to black fixes the problem, but I don't want everything with a black material (there will be point lights eventually). Any ideas? (this is for opengl in case you didn't notice which forum it's in)

Share this post


Link to post
Share on other sites
This is some test code to make sure everything is off:

static GLfloat dummy[4] = {0.0, 0.0, 0.0, 1.0};
for( int i = GL_LIGHT0; i <= GL_LIGHT7; i++ )
{
glLightfv(i, GL_AMBIENT, dummy);
glLightfv(i, GL_DIFFUSE, dummy);
glLightfv(i, GL_POSITION,dummy);
glLightfv(i, GL_SPECULAR,dummy);
glDisable(i);
}

I wouldn't normally iterate through them like this, but I checked the header and they're all in order (this is quick and dirty testing).

I don't know what other source to show you. There's a lot more! If there's anything in particular you'd like to see I'll post it. At this point all light should be completely off, but it's not for some reason.

I'll put some screenshots up after I've tried some things. The only spot I have to put them right now is my google page. All I'm seeing is a very subtle ambient light in the scene, probably close to the opengl default of (0.2, 0.2, 0.2).

Share this post


Link to post
Share on other sites
Screenshot here:
http://thrump.googlepages.com/home

I'm going to try the nehe lighting tutorial to simplify the problem.

Share this post


Link to post
Share on other sites
I think for setting the light to black you have to set the fourth light value to 0.0 (i.e. {0.0, 0.0, 0.0, 0.0} ).

Edit: err, I think I'm bein' stupid. :P Heh. Umm, I think I'm thinkin' of something with material properties like you mentioned... Hrm...

Share this post


Link to post
Share on other sites
This is odd.
'glDisable' should work fine.
Have you tried disabling the lights manually, rather than using a loop?
Strange advice, I know, but try it anyway.

Try replacing '<=' with a '!='.

Share this post


Link to post
Share on other sites
This is very weird, but I figured it out (sort of).

You wouldn't normally see this behavior, as the default material value for ambient light is 0.2 across the board. (0.8 diffuse). I was setting them both to 1.0. Note: this is the material, not the light I'm setting.

This could be my graphics card, or a driver problem, but even with all lights turned off, there is still a slight ambient light in the scene. I got this behavior even with Nehe's lesson 6. With a material value of 0.2 ambient, it's hardly noticable (but you CAN still see it). With my material ambient of 1.0, it was more obvious.

I'm going to retweak my lighting values to see if I can get it looking good with 0.2 ambient materials. I'll try it on my system at work on Monday to see if it's a gfx card thing.

Share this post


Link to post
Share on other sites
I was about to ask you to send me your program to see if it has the problem on my system.
Driver bug, I suspect.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      627754
    • Total Posts
      2978947
  • Similar Content

    • By DelicateTreeFrog
      Hello! As an exercise for delving into modern OpenGL, I'm creating a simple .obj renderer. I want to support things like varying degrees of specularity, geometry opacity, things like that, on a per-material basis. Different materials can also have different textures. Basic .obj necessities. I've done this in old school OpenGL, but modern OpenGL has its own thing going on, and I'd like to conform as closely to the standards as possible so as to keep the program running correctly, and I'm hoping to avoid picking up bad habits this early on.
      Reading around on the OpenGL Wiki, one tip in particular really stands out to me on this page:
      For something like a renderer for .obj files, this sort of thing seems almost ideal, but according to the wiki, it's a bad idea. Interesting to note!
      So, here's what the plan is so far as far as loading goes:
      Set up a type for materials so that materials can be created and destroyed. They will contain things like diffuse color, diffuse texture, geometry opacity, and so on, for each material in the .mtl file. Since .obj files are conveniently split up by material, I can load different groups of vertices/normals/UVs and triangles into different blocks of data for different models. When it comes to the rendering, I get a bit lost. I can either:
      Between drawing triangle groups, call glUseProgram to use a different shader for that particular geometry (so a unique shader just for the material that is shared by this triangle group). or
      Between drawing triangle groups, call glUniform a few times to adjust different parameters within the "master shader", such as specularity, diffuse color, and geometry opacity. In both cases, I still have to call glBindTexture between drawing triangle groups in order to bind the diffuse texture used by the material, so there doesn't seem to be a way around having the CPU do *something* during the rendering process instead of letting the GPU do everything all at once.
      The second option here seems less cluttered, however. There are less shaders to keep up with while one "master shader" handles it all. I don't have to duplicate any code or compile multiple shaders. Arguably, I could always have the shader program for each material be embedded in the material itself, and be auto-generated upon loading the material from the .mtl file. But this still leads to constantly calling glUseProgram, much more than is probably necessary in order to properly render the .obj. There seem to be a number of differing opinions on if it's okay to use hundreds of shaders or if it's best to just use tens of shaders.
      So, ultimately, what is the "right" way to do this? Does using a "master shader" (or a few variants of one) bog down the system compared to using hundreds of shader programs each dedicated to their own corresponding materials? Keeping in mind that the "master shaders" would have to track these additional uniforms and potentially have numerous branches of ifs, it may be possible that the ifs will lead to additional and unnecessary processing. But would that more expensive than constantly calling glUseProgram to switch shaders, or storing the shaders to begin with?
      With all these angles to consider, it's difficult to come to a conclusion. Both possible methods work, and both seem rather convenient for their own reasons, but which is the most performant? Please help this beginner/dummy understand. Thank you!
    • By JJCDeveloper
      I want to make professional java 3d game with server program and database,packet handling for multiplayer and client-server communicating,maps rendering,models,and stuffs Which aspect of java can I learn and where can I learn java Lwjgl OpenGL rendering Like minecraft and world of tanks
    • By AyeRonTarpas
      A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

      -What I'm using:
          C++;. Since im learning this language while in college and its one of the popular language to make games with why not.     Visual Studios; Im using a windows so yea.     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.  
      -Questions
      Knowing what we want in the engine what should our main focus be in terms of learning. File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code. Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?  
    • By ferreiradaselva
      Both functions are available since 3.0, and I'm currently using `glMapBuffer()`, which works fine.
      But, I was wondering if anyone has experienced advantage in using `glMapBufferRange()`, which allows to specify the range of the mapped buffer. Could this be only a safety measure or does it improve performance?
      Note: I'm not asking about glBufferSubData()/glBufferData. Those two are irrelevant in this case.
    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
  • Popular Now