I am trying to make a 3d car race in iphone using OPENGL ES 1.x.
I do not know how to draw the background sky in my scene. I tried using only planes for background but where should i placed that plane? I mean if i placed that plane outside the whole track then the frustum is not so big to show that planes in the scene.
Any suggestions will be of great help.
You can make a small skysphere or box, as suggested by Davido and turbovonce's link, which is centered around the viwer and fits into the frustum. You draw this first, without writing into the depth buffer. Then you draw the other stuff and as the skybox has not written to depth buffer it is just overwritten, except the parts where no scene objects are rendered, which are exactly the parts of the image where the sky should be visible.
You want a sky dome. Take a look at this website, it contains tons of references that should help you.
http://www.vterrain.org/Atmosphere/
Create a sphere in a 3d modeling app such as Maya or Blender and map a sky texture to the sphere. Export the model then load the model and its texture into the app, place in the scene. You should now have a background sky rendering in your game.
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I want to render a cube similar to .
My problem is how to render the face projections.
I tried using Reflector, but it is tricky to size and position so it captures just the face that I want, and also shows the sides.
I also saw I can use a separate canvas to render (I imagine using an orthographic camera), but I wish for everything to be in the same canvas. I saw an example with multiple views, but it seems that they can't be positioned behind.
So, is there a way to achieve this?
One possible approach to solve the issue:
Setup an orthographic camera such that its frustum encloses the cube. You can then position the camera in front of each side of the cube, use lookAt( cube.position ) to orient it properly and then render the scene into a render target. You need one render target per side. You can then use it as a texture for the respective plane mesh.
There is an official live example that demonstrates how RTT (render-to-texture) is done with three.js. Try to use it as a code template for your own app.
https://threejs.org/examples/#webgl_rtt
I'm working with an orthographic view in three.js/WebGL renderer, and I want a magnifying glass that tracks with the user mouse. I'm looking for the best way of doing this that's efficient.
When working with html5 canvas raw commands, this was easy: I simply defined a circular clip region, zoomed my coordinates, and re-drew the whole scene. With 3d objects, it's less obvious how do to it.
The method I've found so far is to do the following:
Define a second camera that looks into the zoomed region. Set the orthographic clip coordinates to be small so that it doesn't need to do much work
Create a THREE.WebGLRenderTarget
Tell the renderer and all my line textures that the resolution is about to change
Render the scene into the RenderTarget
Add a CircleGeometry as a MeshObject at the spot at the mouse position (in world coordinate but above the rest of the scene, close to the camera). Call this the lens.
Give the lens the WebGLRenderTarget as a texture.
Go back to my default camera, reset all my resolution parameters, and redraw the scene with the 'lens' object added.
This works (see image below) but I'm worried about parts of it:
I have to render twice per frame
Lines don't draw well, because the resolution problems. I have to keep track of all materials that need to know screen resolution and update all of them twice per screen render.
Related problems:
I want to overlay some plot axes on top of this, and possibly gridlines. These would change as the view pans. I'm not sure if I should make these 3d objects, or do it in a 2d canvas context I lay overtop.
I want to overlay some plot lines, and have them show up sensibly in the zoomed view. "Sensible" here is hard to figure out: I don't want them too fat in the zoomed view, but I also don't want to scale them up as much as the image detail (which is being rendered as a texture onto Plane objects behind).
This is a long post, but I'm still new to three.js and looking for good ideas.
Can you please explain the difference between texture and sprite? When we zoom in a sprite, it appears blurry because it's basically an image. Is it the same for a texture?
I read this comment on the image below online:
The background layers are textures and not sprites.
Can someone explain?
Sprites and Textures are both images.
A Sprite is an image that can be used as a 2d object, which have coordinates (x, y) and which you can move, destroy or create during the game.
A Texture is also an image, but that will be used to change the appearence of an object. E.g. you can set a texture for the faces of a cube, a layer (like the background) or even a sprite. But as texture are not objects, you can't move them during the game.
Sprite is the image that is moving related to static images (for example background). Sprites are usually planes (rectangles) with texture on it. Sprites are used in 3D graphics for tricks such as Billboard or Impostor. In 2D games sprites are used instead of moving objects and also as backgrounds.
Texture is an raster image that is to be projected on polygonal object. It worth using textures each time when using polygons is expensive for given objects details (for example bullet dots)
I need to draw transparent 2D sprites in a 3D world. I tried rendering a QUAD, texturing it(using slick_util) and rotating it to face the camera, but when there are many of them the transparency doesn't really work. The sprite closest to the camera will block the ones behind it if it's rendered before them.
I think it's because OpenGL only draws the object that is closest to the viewer without checking the alpha value.
This could be fixed by sorting them from furthest away to closest but I don't know how to do that
and wouldn't I have to use math.sqrt to get the distance? (I've heard it's slow)
I wonder if there's an easy way of getting transparency in 3D to work correctly. (Enabling something in OpenGL e.g)
Disable depth testing and render transparent geometry back to front.
Or switch to additive blending and hope that looks OK.
Or use depth peeling.
I would like to play around with testing a 3D map, of sorts. At it's simplest, one flat pane, with map lines etc. drawn onto it, flat (as if I was drawing onto an HTML canvas). But I want that pane to be movable in 3D space.
I know that I can make a flat pane in three.js very simply, but is it possible to implement some sort of 'custom texture' that would allow me to programmatically draw onto this pane?
It is called render-to-texture in webGL.
Three.js provides WebGLRenderTarget which can be used as image source for further textures. You render your scene to WebGLRenderTarget instead of main WebGL screen. Then you use this WebGLRenderTarget as image source for the texture.
A lot of 2D post-processing works like this. They render the world to 2D texture, then use fragment shaders to apply per-pixel postprocessing code, like blurring.
For examples, see e.g. http://mrdoob.github.com/three.js/examples/webgl_postprocessing.html
It renders the scene for 2D postprocessing, but the theory is the same.
Here is the WebGLRenderTarget setup code:
https://github.com/mrdoob/three.js/blob/master/examples/js/postprocessing/EffectComposer.js#L14