Sign in to follow this  

OpenGL OpenGL lighting issue...

Recommended Posts

Calefaction    174
So I posted this over in the Graphics Programming forum, was trying to fish for a more general, non-OpenGL answer...but considering I am using OpenGL for this application, perhaps I will fish here for an answer :) Here is the situation. I am moving our current engine towards using hardware dynamic lighting, rather then spherical harmonics. I am having a wierd problem though. I am pretty sure I have set everything up correctly and that I am passing all the required data, but I am obviously not because I get this effect: My first thought was that the normals are not being sent correctly, but I have stepped through the code and all the normals are there and being passed to the OpenGL using glNormalPointer. Also, GL_NORMAL_ARRAY is enabled, so OpenGL should be setup to except those normals. I have set up the light model settings, as well as GL_LIGHT0's direction and color. GL_LIGHTING and GL_LIGHT0 are enabled. Also of note is the fact my trees (which are drawn in the second step of rendering, the alpha blend step) are drawing correctly. Odd at best :) Possibly also of note is that glColorModel is set to GL_AMBIENT_AND_DIFFUSE (such that those colors are taken from a call to glColor). So, given the screenshot, does anyone have any ideas as to what is causing that? (Oh, and I would post code, but the various snippets are strewn about the engine and are hard to collate in to anything useful).

Share this post

Link to post
Share on other sites
Calefaction    174
Hrm, I think I may see the problem. When using glNormalPointer, should I be giving it each vertex normal, or just the face normals for the faces defined by the vertices passed in via glVertexPointer?

Share this post

Link to post
Share on other sites
janharal    138
glNormalPointer wants vertex-normals. Normals can be flipped just by inverting them. You might want to try moving the lightsource around to see if there's any reaction. Your lightsource position seems a bit strange to be, but that depends on your geometry of course.

Share this post

Link to post
Share on other sites
Calefaction    174
Okay, moved my light position to 1.0, 1.0, 0.0, 0.0 (I read somewhere it is a sane default value). Things appear lit now, but I am getting wierd "splotching" effects with the shading and it's very "unsmooth", especially when models walk. I am guessing this is the normals being incorrectly passed or calculated somehow...

Share this post

Link to post
Share on other sites
Calefaction    174
I seem to have cleared up most of the problems :) It was color issues, I wasn't setting proper ambient colors in all places. So shading was appearing very dark and blotchy when it shouln't have. This all seems to be working as expected now :)

Next up, dark maps for the terrain :)

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  

  • Similar Content

    • By cebugdev
      hi all,

      i am trying to build an OpenGL 2D GUI system, (yeah yeah, i know i should not be re inventing the wheel, but this is for educational and some other purpose only),
      i have built GUI system before using 2D systems such as that of HTML/JS canvas, but in 2D system, i can directly match a mouse coordinates to the actual graphic coordinates with additional computation for screen size/ratio/scale ofcourse.
      now i want to port it to OpenGL, i know that to render a 2D object in OpenGL we specify coordiantes in Clip space or use the orthographic projection, now heres what i need help about.
      1. what is the right way of rendering the GUI? is it thru drawing in clip space or switching to ortho projection?
      2. from screen coordinates (top left is 0,0 nd bottom right is width height), how can i map the mouse coordinates to OpenGL 2D so that mouse events such as button click works? In consideration ofcourse to the current screen/size dimension.
      3. when let say if the screen size/dimension is different, how to handle this? in my previous javascript 2D engine using canvas, i just have my working coordinates and then just perform the bitblk or copying my working canvas to screen canvas and scale the mouse coordinates from there, in OpenGL how to work on a multiple screen sizes (more like an OpenGL ES question).
      lastly, if you guys know any books, resources, links or tutorials that handle or discuss this, i found one with marekknows opengl game engine website but its not free,
      Just let me know. Did not have any luck finding resource in google for writing our own OpenGL GUI framework.
      IF there are no any available online, just let me know, what things do i need to look into for OpenGL and i will study them one by one to make it work.
      thank you, and looking forward to positive replies.
    • By fllwr0491
      I have a few beginner questions about tesselation that I really have no clue.
      The opengl wiki doesn't seem to talk anything about the details.
      What is the relationship between TCS layout out and TES layout in?
      How does the tesselator know how control points are organized?
          e.g. If TES input requests triangles, but TCS can output N vertices.
             What happens in this case?
      In this article,
      the isoline example TCS out=4, but TES in=isoline.
      And gl_TessCoord is only a single one.
      So which ones are the control points?
      How are tesselator building primitives?
    • By Orella
      I've been developing a 2D Engine using SFML + ImGui.
      Here you can see an image
      The editor is rendered using ImGui and the scene window is a sf::RenderTexture where I draw the GameObjects and then is converted to ImGui::Image to render it in the editor.
      Now I need to create a 3D Engine during this year in my Bachelor Degree but using SDL2 + ImGui and I want to recreate what I did with the 2D Engine. 
      I've managed to render the editor like I did in the 2D Engine using this example that comes with ImGui. 
      3D Editor preview
      But I don't know how to create an equivalent of sf::RenderTexture in SDL2, so I can draw the 3D scene there and convert it to ImGui::Image to show it in the editor.
      If you can provide code will be better. And if you want me to provide any specific code tell me.
    • By Picpenguin
      I'm new to learning OpenGL and still learning C. I'm using SDL2, glew, OpenGL 3.3, linmath and stb_image.
      I started following through and got through it until I had to load models. The problem is, it uses Assimp for loading models. Assimp is C++ and uses things I don't want in my program (boost for example) and C support doesn't seem that good.
      Things like glVertexAttribPointer and shaders are still confusing to me, but I have to start somewhere right?
      I can't seem to find any good loading/rendering tutorials or source code that is simple to use and easy to understand.
      I have tried this for over a week by myself, searching for solutions but so far no luck. With tinyobjloader-c and project that uses it, FantasyGolfSimulator, I was able to actually load the model with plain color (always the same color no matter what I do) on screen and move it around, but cannot figure out how to use textures or use its multiple textures with it.
      I don't ask much: I just want to load models with textures in them, maybe have lights affect them (directional spotlight etc). Also, some models have multiple parts and multiple textures in them, how can I handle those?
      Are there solutions anywhere?
      Thank you for your time. Sorry if this is a bit confusing, English isn't my native language
    • By dpadam450
      FINALLY, upgrading my engine to openGL 4. I was having some trouble so I started with a stripped down application and was wondering if VAO's are required, because I have a sample working, but if I remove the VAO then it doesn't seem to like drawing my triangle.
  • Popular Now