OpenGL ES questions regarding 2D mixed with 3D

Posts: 75
Joined: 2009.01
Post: #1
Just dove into OpenGL ES 2 days back and got quite a few done.
I am trying to create something similar to the newer generation pokemon games (diamond/pearl/platinum) but so far all I get is something that comes a bit close to it.

Basically all I want to ask:

How do you create that top down view effect.
I cannot quite get it and when it "looks" alright, it isn't when I move around the map.
Any advice?
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Posts: 320
Joined: 2003.06
Post: #2
It sounds like you probably want to play with the field of view. Having a very narrow field of view and making the objects smaller or the camera further away will get closer to having an orthographic projection. If you don't want any perspective at all there is no reason why you can't use glOrtho with 3D objects.

Chopper, iSight Screensavers, DuckDuckDuck:
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Posts: 75
Joined: 2009.01
Post: #3
Thing is, I've been playing around with the field of view and still cannot produce the effect I'm looking for.
Maybe it's because I don't understand glFrustumf fully but the fields I put it are from jeffs blog.
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Posts: 1,560
Joined: 2003.10
Post: #4
glFrustum can be pretty confusing. gluPerspective is easier to visualize, but since glu isn't included with OpenGL ES, you'd need to do the matrix math yourself, then multiply the projection matrix by the result. There's an implementation of something nearly identical to gluPerspective in my matrix tutorial (see Matrix_applyPerspective).
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Posts: 3,570
Joined: 2003.06
Post: #5
Here's my gluPerspective replacement:
void setPerspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
    GLfloat xmin, xmax, ymin, ymax;

    ymax = zNear * tanf(fovy * M_PI / 360.0f);
    ymin = -ymax;
    xmin = ymin * aspect;
    xmax = ymax * aspect;

    glFrustumf(xmin, xmax, ymin, ymax, zNear, zFar);
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Posts: 75
Joined: 2009.01
Post: #6
Thanks, i'll look at the tutorial.
I'll give that code a try too jake.
One thing I forgot to mention, I use gluLookAt.
from what I understand, the first three parameters for gluLookAt are the x,y,z coordinates for where you are looking "from".
The second three parameters are where you are looking "to".
I am not sure what the last three parameters do as I get some pretty confusing results.

Do you thing gluLookAt will help in achieving this top down view effect?
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