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# OpenGL opengl and side scrolling

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I''m trying to make a program that follows a character centered on the main screen using openGL. My initial idea was to use glTranslate to move the screen axis based on how much the character moves. But for some reason this doesn''t work. Also, the game is 2D, so there is only x and y axis movement. Is there an easier way to make the screen move?

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glTranslate should work! both in perspective or in orthogonal mode..

its the simplest and fastest(in a simple 2d tile/billboard scroller) to move stuff with opengl!

Other methods would require you to recalc every vertex you send to OGL every frame ,if CPU power dont is a problem, this should be as fast as glTranslate (if you send every vertex to OGL every frame anyway), but then you talk about simplicity, and glTranslate wins again!

If you have a advanced culling method, you might need to do some calculations even if you use glTranslate, and simplicity might fall as a argument, but why not create a method, based on that you use glTranslate!( = fast and simple)

look it up, and learn it well! its the best and simplest way! (for a simple 2d tile/billboard scroller)

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My OpenGL class at www.icarusindie.com in the DevZone includes a method for calculating 3D coordinates from 2D coordinates. I prefer doing it that way since I still want pespective. The method just gives me an easier way to specify where to start drawing.

Ben

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i don''t see where in your opengl class (http://www.icarusindie.com/devzone/mysource/OpenGLclass/Data/ ?) is that method

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Since my 3D to 2D methods are apparently not in the version I released, here it is.

GLvoid oglClass::SetTranslate2D(float x, float y, float z)
{
glTranslatef(x*4.0f/(float)screenW-2.0f,1.5f-y*3.0f/(float)screenH,z-3.63f);
}

GLvoid oglClass::ReSizeGLScene(GLsizei width, GLsizei height)
{
if (height==0)
height=1;

glViewport(0,0,width,height);

glMatrixMode(GL_PROJECTION);

// Calculate The Aspect Ratio Of The Window

gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

glMatrixMode(GL_MODELVIEW);

screenH=(float)height;
screenW=(float)width;
xratio=1024.0f/screenW;
yratio=768.0f/screenH;
}

The equations I use must use the gluPerspective settings I use above. xration and yratio are then applied to any shapes you want to remain the same number of pixels regardless of the resolution the user sets.

With the above 1 unit is 256 pixels so you can draw your primitives accordingly.

My OpenGL class will be rereleased some time in the future with MD2 model support and a particle system and whatever else I need for my current project.

Ben

IcarusIndie.com

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