Is there any way to remove or hide radial segments from ConeBufferGeometry, CylinderBufferGeometry etc ? I'm new to 3D and three.js so I don't really know is it some crucial part of these geometries or I can hide it.
What do you mean? What are the "radial segments"? If you remove the outer surface all you're left with is a disc from the bottom of a cone or 2 discs from the ends of the cylindar.
If you wanted just a disc use a CircleBufferGeometry. If you wanted the ends gone then read the docs. They make it pretty clear there is an option to remove the ends
https://threejs.org/docs/#api/en/geometries/ConeBufferGeometry
https://threejs.org/docs/#api/en/geometries/CylinderBufferGeometry
Otherwise you can make your own custom geometry
Related
I want to keep scale when i rotate verticles. But it is getting smaller after rotation. Picture 3 and 4:
How can i keep it same size ?
Rotate is the wrong tool, if you look directly at the circular face after rotating it will remain circular, where the result you are after will become an oval.
The tool you want is called shear, which will move the top vertices the opposite way to the bottom vertices without altering the height. You can find shear in Mesh->Transform->Shear or the shortcut Ctrl-Alt-Shift-S. The shear tool transforms based on the view so you will want to be in side view when you use it.
Another option would be to use the knife tool to cut a line through your tube.
You can also position a plane over the tube and use intersect (Knife).
I'm interested in drawing a stardome in THREE.js using either mesh points or a particle system.
I don't want the camera to be able to move any closer to any part of the stardome, since the stars are effectively at infinite distance.
I can think of a couple of ways to do this:
A very large mesh (or very large point/particle distances)
Camera and stardome have their movement exactly linked.
Is there any way to specify a mesh, point, or particle system is automaticaly rendered at infinite distance so it is always drawn behind any foreground objects?
I haven't used three.js, but my guess is no. OpenGL camera's need a "near clipping plane" and "far clipping plane", which effectively denote the minimum and maximum distance that it'll render things in. If you've played video games where you move too close to a wall and start to see through it, or see things in the distance suddenly vanish as you move away, those were probably the clipping planes at work.
The workaround is usually one of 2 ways:
1) Set the far clipping plane distance as high as it'll let you go. I don't know what data type three.js would use for this, but my guess is a 32-bit float.
2) Render it in "layers". Render all the stars first before anything else in the scene.
Option 2 is the one I usually use.
Even if you used option 1, you would still synchronize the position of the camera and skybox.
If you do not depth cull, draw the skybox first and match its position, but not rotation, to the camera.
Also disable lighting on the skybox. Instead, bake an ambience directly into its texture.
You're don't want things infinitely away, you just want them not to move with respect to the viewer and to not appear in front of things. The best way to do that is to prevent the viewer from getting closer to them which produces the illusion of the object being far away. The second thing is to modify your depth culling function so that the skybox is always considered further away than whatever you are currently drawing.
If you create a very large mesh object, you'll have to set your camera's far plane large enough to include the mesh which means you'll end up drawing things that you really do want to cull.
How can I set a black color to the whole screen, excluding a shaperenderer circle? The circle is basically my game world, anything that leaves it shouldn't be visible. Is there some way to create a reverse circle pixmap (eg..A circle, but inverted) to overlay everything except for the circle game area? Or maybe a way to clear the screen, excluding parts? Thanks!
You could try the approach you mentioned in the comments. Using a black image with a circular hole in it. Then have each assigned to a different camera much in the same way you would set up a HUD in libgdx.
You might want to take a look at shaders, this approach is really flexible and lets you even control how rapid the transition is. Just the basics of GLSL should be sufficient.
https://www.youtube.com/watch?v=caQZKeAYgD8 Here's a decent tutorial.
I just started to fiddle around with WebGL and three.js.
I would really like to create a thick line, which has rounded corners and endings. (see example picture)
Unfortunately I see that firstly the LineBasicMaterial's linecap property does not really work.
Three.js LineBasicMaterial
I started to think about using a tube, but then I think I will still not get a round cap...
Does someone have any ideas how I could create a line in the picture above? It does not necessarily have to made with three.js but WebGL would be a requirement. (I also want to animate this line further on...)
Thanks for any hints.
Cheers
There are a couple ways to draw 3d volumetric lines. The first is to do a vertex expansion in the shader. This is what the links in the comments do. Here is another one in case you need more material: http://codeflow.org/entries/2012/aug/05/webgl-rendering-of-solid-trails/.
Unfortunately it have visual artifacts when the line segment is viewed directly heads on. Check out the demo here: http://codeflow.org/webgl/trails/www/. Spin the scene around and you will notice some line segments facing directly towards the camera will spin rapidly. It looks a lot worse with a less noisy texture btw. If this is fine with you this is probably the preferred option.
The 2nd option is to just dynamically generate a capsule mesh for each line segment. Not much to say about it, beyond that this is a simple, abet somewhat inefficient method.
The 3rd option is to do a limited kind of ray tracing in the shader. Calculate the distance between the line segment and the fragment being shaded and we can use that to determine the appropriate color. Here is a link for that. Geometry shader is not currently supported in the webgl but there is nothing stopping you from generating the bounding line cuboid via javascript. Oh and if you need soft lines you probably need the blend_minmax extension. Probably the hardest method to setup but can be viewed at any angle and very customize-able compared to the other 2 methods.
When several objects overlap on the same plane, they start to flicker. How do I tell the renderer to put one of the objects in front?
I tried to use .renderDepth, but it only works partly -
see example here: http://liveweave.com/ahTdFQ
Both boxes have the same size and it works as intended. I can change which of the boxes is visible by setting .renderDepth. But if one of the boxes is a bit smaller (say 40,50,50) the contacting layers are flickering and the render depth doesn't work anymore.
How to fix that issue?
When .renderDepth() doesn't work, you have to set the depths yourself.
Moving whole meshes around is indeed not really efficient.
What you are looking for are offsets bound to materials:
material.polygonOffset = true;
material.polygonOffsetFactor = -0.1;
should solve your issue. See update here: http://liveweave.com/syC0L4
Use negative factors to display and positive factors to hide.
Try for starters to reduce the far range on your camera. Try with 1000. Generally speaking, you shouldn't be having overlapping faces in your 3d scene, unless they are treated in a VERY specific way (look up the term 'decal textures'/'decals'). So basically, you have to create depth offsets, and perhaps even pre sort the objects when doing this, which all requires pretty low-level tinkering.
If the far range reduction helps, then you're experiencing a lack of precision (depending on the device). Also look up 'z fighting'
UPDATE
Don't overlap planes.
How do I tell the renderer to put one of the objects in front?
You put one object in front of the other :)
For example if you have a camera at 0,0,0 looking at an object at 0,0,10, if you want another object to be behind the first object put it at 0,0,11 it should work.
UPDATE2
What is z-buffering:
http://en.wikipedia.org/wiki/Z-buffering
http://msdn.microsoft.com/en-us/library/bb976071.aspx
Take note of "floating point in range of 0.0 - 1.0".
What is z-fighting:
http://en.wikipedia.org/wiki/Z-fighting
...have similar values in the z-buffer. It is particularly prevalent with
coplanar polygons, where two faces occupy essentially the same space,
with neither in front. Affected pixels are rendered with fragments
from one polygon or the other arbitrarily, in a manner determined by
the precision of the z-buffer.
"The renderer cannot reposition anything."
I think that this is completely untrue. The renderer can reposition everything, and probably does if it's not shadertoy, or some video filter or something. Every time you move your camera the renderer repositions everything (the camera is actually the only thing that DOES NOT MOVE).
It seems that you are missing some crucial concepts here, i'd start with this:
http://www.opengl-tutorial.org/beginners-tutorials/tutorial-3-matrices/
About the depth offset mentioned:
How this would work, say you want to draw a decal on a surface. You can 'draw' another mesh on this surface - by say, projecting a quad onto it. You want to draw a bullet hole over a concrete wall and end up with two coplanar surfaces - the wall, the bullet hole. You can figure out the depth buffer precision, find the smallest value, and then move the bullet hole mesh by that value towards the camera. The object does not get scaled (you're doing this in NDC which you can visualize as a cube and moving planes back and forth in the smallest possible increment), but does translate in depth direction, ending up in front of the other.
I don't see any flicker. The cube movement in 3D seems to be super-smooth. Can you try in a different computer (may be faster one)? I used Chrome on Macbook Pro.