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• I wasn't sure if this would be the right place for a topic like this so sorry if it isn't.
I'm currently working on a project for Uni using FreeGLUT to make a simple solar system simulation. I've got to the point where I've implemented all the planets and have used a Scene Graph to link them all together. The issue I'm having with now though is basically the planets and moons orbit correctly at their own orbit speeds.
I'm not really experienced with using matrices for stuff like this so It's likely why I can't figure out how exactly to get it working. This is where I'm applying the transformation matrices, as well as pushing and popping them. This is within the Render function that every planet including the sun and moons will have and run.
if (tag != "Sun") { glRotatef(orbitAngle, orbitRotation.X, orbitRotation.Y, orbitRotation.Z); } glPushMatrix(); glTranslatef(position.X, position.Y, position.Z); glRotatef(rotationAngle, rotation.X, rotation.Y, rotation.Z); glScalef(scale.X, scale.Y, scale.Z); glDrawElements(GL_TRIANGLES, mesh->indiceCount, GL_UNSIGNED_SHORT, mesh->indices); if (tag != "Sun") { glPopMatrix(); } The "If(tag != "Sun")" parts are my attempts are getting the planets to orbit correctly though it likely isn't the way I'm meant to be doing it. So I was wondering if someone would be able to help me? As I really don't have an idea on what I would do to get it working. Using the if statement is truthfully the closest I've got to it working but there are still weird effects like the planets orbiting faster then they should depending on the number of planets actually be updated/rendered.

• Hello everyone,
I have problem with texture

• Hello everyone
For @80bserver8 nice job - I have found Google search. How did you port from Javascript WebGL to C# OpenTK.?
I have been searched Google but it shows f***ing Unity 3D. I really want know how do I understand I want start with OpenTK But I want know where is porting of Javascript and C#?

Thanks!
• By mike44
Hi
I draw in a OpenGL framebuffer. All is fine but it eats FPS (frames per second), hence I wonder if I could execute the framebuffer drawing only every 5-10th loop or so?
Many thanks

• By cebugdev
hi all,
how to implement this type of effect ?
Also what is this effect called? this is considered volumetric lighting?
what are the options of doing this?
a. billboard? but i want this to have the 3D effect that when we rotate the camera we can still have that 3d feel.
b. a transparent 3d mesh? and we can animate it as well?

2. how to implement things like fireball projectile (shot from a monster) (billboard texture or a 3d mesh)?

Note: im using OpenGL ES 2.0 on mobile.

thanks!

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# OpenGL opengl and side scrolling

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## Recommended Posts

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);	glLoadIdentity();	// Calculate The Aspect Ratio Of The Window	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();	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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