Sign in to follow this  
phil67rpg

OpenGL opengl game

Recommended Posts

phil67rpg    443

well I am attempting to render the aliens on the screen, I want to draw the alien to the screen and move to the right and then erase the sprite and draw a new  sprite and moves the sprite to the right again. basically I want to draw a sprite and erase it and redraw a different sprite and then erase it and then draw the previous sprite and have all the sprite to move to the right.

Share this post


Link to post
Share on other sites
BlueSpud    650

well I am attempting to render the aliens on the screen, I want to draw the alien to the screen and move to the right and then erase the sprite and draw a new  sprite and moves the sprite to the right again. basically I want to draw a sprite and erase it and redraw a different sprite and then erase it and then draw the previous sprite and have all the sprite to move to the right.

Thats not exactly what you want to do. Create an object for each alien:

class Invader
{
public:
float x,y,z;
void update()

};

Then create the invaders in whatever way you want best to handle them.

Make a callback for glutIdleFunc().

Put in that callback:

//call onUpdate() for all the invaders
updateInvaders()
//draw a new frame
glutPostRedDisplay();

In the onUpdate() for the invaders, move them left and right using their positions. The render for them would look something like this:


void invader::render()
{
glTranslatef(-x,-y,-z);
//render sprite
renderSprite();
}

Hope that helps

Share this post


Link to post
Share on other sites
lask1    1144

If you want to update multiple enemies and have a list of them and run a for loop to do the update for each one. You can do this by either using a linked list or...not sure if any one would get mad at me for saying this but you could use a vector.

These are both basically dynamic lists like an array that can change in size...be careful with deleting objects while a loop is running.

 

http://www.cplusplus.com/reference/vector/vector/

 

http://www.cplusplus.com/articles/Lw6AC542/

 

Hope this helps.

Share this post


Link to post
Share on other sites
Solid_Spy    708

so I should use a vector? I am somewhat familiar with vectors.

It depends, you could make your own linked list, but only if it is absolutely necessary. The std::vector does have some overhead, but shouldn't be noticable for this game.

Edited by Solid_Spy

Share this post


Link to post
Share on other sites
BlueSpud    650

 

so I should use a vector? I am somewhat familiar with vectors.

It depends, you could make your own linked list, but only if it is absolutely necessary. The std::vector does have some overhead, but shouldn't be noticable for this game.

 

If he stored the textures outside the object, just not drawing them and still allocating the RAM for each invader wouldn't be a big deal, he could just clear the vector at the end of the level and it wouldn't be a huge performance problem. 

Share this post


Link to post
Share on other sites
BlueSpud    650

well I got the collision detection to work with the ufo at the top of the screen, but I also want the bullet to collide with the aliens, and then turn off the aliens.

Because your not really shooting in diagonals, as far as I can tell, check into Axis aligned bounding box collisions, they're pretty easy ex:

struct box
{
float maxx,maxy,minx,miny;
};
bool collision(box* one, box* two)
if (one->maxx < two->minx || one->mazy < two->miny || one->minx > two->maxx || one->miny > two->maxy)
// no collision in any of these cases
return false;
//defaults to colliding
else return true

Of course, you would need to constantly update the boxes position, so you might want to add some kind of offset in there somewhere and add them onto the max,min,etc during the test. If you want something for oriented bounding boxes, boxes that aren't axis aligned, in other words, rotated, look into the separating axis theorem. Its a bit slower, but its fairly simple to implement and its almost pixel perfect.

Share this post


Link to post
Share on other sites
BlueSpud    650

so how do I do multiple collision detection using AABB.

AABB being good is kind of ipso-facto, only if you want axis aligned boxes. If you want to test all the boxes against your bullet, you don't want to test all of them in say a loop, while your game is pretty simple and you probably wouldn't notice the difference, you should do at least 2 steps. There are a lot of approaches to the 2 step thing, for more complicated collision detection, there are even upwards of 3. By no means am I an expert, but this is what I would do:

1. loop through all the bounding boxes and check if the center of the bullet is within a relatively small distance to the center of each box. If it is, add it to the next step to be tested for the AABB collision.
2. loop through all the boxes that were passed down and as soon as you find a collision, stop the loop because there is no need to keep checking for possible collisions.

 

To reiterate, this isn't really necessary, but it is going to save you quite a bit of CPU time if you have 30 or 40 enemies, or you are testing multiple bullets per frame.

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 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. 
       
      Thanks
    • 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,
      http://www.informit.com/articles/article.aspx?p=2120983
      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.
      Thanks!
  • Popular Now