This topic is now archived and is closed to further replies.


OpenGL OpenGL Game Programming

Recommended Posts

Cherub    122
Hi, This question is for those who read this book: in the SimpEngine, described in the book, what do I need to do to separate the models from the terrain? Because if I don''t draw the terrain, the models aren''t drawn.... Thanks

Share this post

Link to post
Share on other sites
noisecrime    817
Hi Cherub,

Well it sounds like you''ll need to read the book again.
The reason why disabling the terrain, disables all other models is in there.

Its all to do with nodes and objects.
The concept of the simplengine is that every 3D object/model is dervived from the node/object base classes.

This allows for all objects to be linked together in a heirachy, the idea being to simplify the code for generating 3D worlds.

In this case the terrain is the root node, the player and enemy models are attached to it. So when calling Terrain draw function, its actually calling the object ondraw function. This function draws the model (terrain), then checks if there are any child nodes (players and enemies), if true it passes on the draw command to these children, who in turn will pass the command to thier children (e.g player - missile would be obvious one, but i''ve not got as far as checking if thats true).

If you want to disable the terrain from drawing then I would simply do

void CTerrain::OnDraw(CCamera *camera)

// Rest of original function code
int z, x;


However if you do this all the models will be black!
This is because for some odd reason a number of important openGL states are set in the terrain on draw, which actually apply to the drawing off all models. So instead of adding the ''return'' at the start of the above function, place it after all the openGL states have been set.

This should achieve what you asked, however please note its hard to find the enemies without the terrain as you have no visual reference to allow you to search - you just have to move around randomly until you find one. You should still see your rockets firing though.

Finally if you make a debug build make sure you include the models folder and all the sound/bitmap files into the debug folder, otherwise the engine what be able to find them (although it doesn''t crash if it doesn''t find them - you just don''t see any models)

Hope this helps

Share this post

Link to post
Share on other sites
GalaxyQuest    122
Simple solution:
Create 2 root nodes:
One for the terrain as it''s own node.
One which is for all your objects.

An advanced solution might be:
Use a root node for terrain.
Use a quadtree structure, which has a root node in each quadtree section. Then, as you run through your quadtree for visible quadtree sections, you render the root object nodes as well.

Hope you get it.

- john

Share this post

Link to post
Share on other sites

  • Similar Content

    • By pseudomarvin
      I assumed that if a shader is computationally expensive then the execution is just slower. But running the following GLSL FS instead just crashes
      void main() { float x = 0; float y = 0; int sum = 0; for (float x = 0; x < 10; x += 0.00005) { for (float y = 0; y < 10; y += 0.00005) { sum++; } } fragColor = vec4(1, 1, 1 , 1.0); } with unhandled exception in nvoglv32.dll. Are there any hard limits on the number of steps/time that a shader can take before it is shut down? I was thinking about implementing some time intensive computation in shaders where it would take on the order of seconds to compute a frame, is that possible? Thanks.
    • By Arulbabu Donbosco
      There are studios selling applications which is just copying any 3Dgraphic content and regenerating into another new window. especially for CAVE Virtual reality experience. so that the user opens REvite or CAD or any other 3D applications and opens a model. then when the user selects the rendered window the VR application copies the 3D model information from the OpenGL window. 
      I got the clue that the VR application replaces the windows opengl32.dll file. how this is possible ... how can we copy the 3d content from the current OpenGL window.
      anyone, please help me .. how to go further... to create an application like VR CAVE. 
    • 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.
  • Popular Now