I'm trying to create a fluid simulation on blender 2.92 but after the bake of the fluid, this one is not laying on the floor. It's floating at around 10cm above and also, it stays at 10cm from the walls.
Space between fluid and floor
Space between fluid and walls
Low res render
Does anybody know what I'm setting wrong ? The obstacle is inside a cube which has a solidify modifier applied and set up as Effector / Collision.
Any help will be appreciated
Did
Without having much to look at other than what you had provided, it's the resolution of your domain. When you look at your domain box, there should be a small "cube" in the corner. If you move the cube down under your floor to where the top of the cube is touching the floor, this will fix the gap between the floor and water. Just keep in mind, when you increase that resolution, that cube will get smaller. Meaning, you will need to adjust the position of it yet again. For the walls, you will need to widen your domain until the side of the cube is on the outside of the wall.
Think of the cube as a "safety boundary/perimeter" or something like that. Hopefully that all makes sense?
Related
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.
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.
A quick introduction:
We're developing a positioning system that works the following way. Our camera is situated on a robot and is pointed upwards (looking at the ceiling). On the ceiling we have something like landmarks, thanks to whom we can compute the position of the robot. It looks like this:
Our problem:
The camera is tilted a bit (0-4 degrees I think), because the surface of the robot is not perfectly even. That means, when the robot turns around but stays at the same coordinates, the camera looks at a different position on the ceiling and therefore our positioning program yields a different position of the robot, even though it only turned around and wasn't moved a bit.
Our current (hardcoded) solution:
We've taken some test photos from the camera, turning it around the lens axis. From the pictures we've deduced that it's tilted ca. 4 degrees in the "up direction" of the picture. Using some simple geometrical transformations we've managed to reduce the tilt effect and find the real camera position. On the following pictures the grey dot marks the center of the picture, the black dot is the real place on the ceiling under which the camera is situated. The black dot was transformed from the grey dot (its position was computed correcting the grey dot position). As you can easily notice, the grey dots form a circle on the ceiling and the black dot is the center of this circle.
The problem with our solution:
Our approach is completely unportable. If we moved the camera to a new robot, the angle and direction of tilt would have to be completely recalibrated. Therefore we wanted to leave the calibration phase to the user, that would demand takings some pictures, assessing the tilt parameters by him and then setting them in the program. My question to you is: can you think of any better (more automatic) solution to computing the tilt parameters or correcting the tilt on the pictures?
Nice work. To have an automatic calibration is a nice challenge.
An idea would be to use the parallel lines from the roof tiles:
If the camera is perfectly level, then all lines will be parallel in the picture too.
If the camera is tilted, then all lines will be secant (they intersect in the vanishing point).
Now, this is probably very hard to implement. With the camera you're using, distortion needs to be corrected first so that lines are indeed straight.
Your practical approach is probably simpler and more robust. As you describe it, it seems it can be automated to become user friendly. Make the robot turn on itself and identify pragmatically which point remains at the same place in the picture.
I'm having an issue with back faces (to the light) and shadow mapping that I can't seem to get past. I'm still at the relatively early stages of optimizing my engine, however I can't seem to get there as even with everything hand-tuned for this one piece of geometry it still looks like garbage.
What it is is a skinny wall that is "curved" via about 5 different chunks of wall. When I create my depth map I'm culling front faces (to the light). This definitely helps, but the front faces on the other side of the wall are what seem to be causing the z-fighting/projective shadowing.
Some notes on the screenshot:
Front faces are culled when the depth texture (from the light) is being drawn
I have the near and far planes tuned just for this chunk of geometry (set at 20 and 25 respectively)
One directional light source, coming down on a slight angle toward the right side of the scene, enough to indicate that wall should be shadowed, but mostly straight down
Using a ludicrously large 4096x4096 shadow map texture
All lighting is disabled, but know that I am doing soft lighting (and hence vertex normals for the vertices) even on this wall
As mentioned here it concludes you should not shadow polygons that are back faced from the light. I'm struggling with this particular issue because I don't want to pass the face normals all the way through to the fragment shader to rule out the true back faces to the light there - however if anyone feels this is the best/only solution for this geometry thats what I'll have to do. Considering how the pipeline doesn't make it easy/obvious to pass the face normals through it makes me feel like this isn't the path of least resistance. And note that the normals I am passing are the vertex normals, to allow for softer lighting effects around the edges (will likely include both non-shadowed and shadowed surfaces).
Note that I am having some nasty Perspective Aliasing, but I'm hoping my next steps are to work on cascaded shadow maps, but without fixing this I feel like I'm just delaying the inevitable as I've hand-tightened the view as best I can (or so I think).
Anyways I feel like I'm missing something, so if you have any thoughts or help at all would be most appreciated!
EDIT
To be clear, the wall technically should NOT be in shadow, based on where the light is coming from.
Below is an image with shadowing turned off. This is just using the vertex normals to calculate diffuse lighting - its not pretty (too much geometry is visible) but it does show that some of the edges are somewhat visible.
So yes, the wall SHOULD be in shadow, but I'm hoping I can get the smoothing working better so the edges can have some diffuse lighting. If I need to have it completely in shadow, then if its the shadow map that puts it in shadow, or my code specifically putting it in shadow because the face normal is away, I'm fine with that - but passing the face normal through to my vertex/fragment shader does not seem like the path of least resistance.
Perhaps these will help illustrate my problem better, or perhaps bring to light some fundamental understanding I am missing.
EDIT #2
I've included the depth texture below. You can see the wall in question in the bottom left, and from the screenshot you can see how i've trimmed the depth values to ~0.4->1. This means the depth values of that wall start in the 0.4 range. So its not PERFECTLY clipped for it, but its close. Does that seem reasonable? I'm pretty sure its a full 24 or 32 bit depth buffer, a la DEPTH_COMPONENT extension on iOS. For #starmole, does this help to determine if its a scaling error in my projection? Do you think the size/area covered of my map is too large, hence if it focuses closer it might help?
The problem seems to be that you are
Culling the front faces
Looking at the back face
Not removing the light from the back face because it's actually not lit by the normal - or there is some inaccuracy in the computation
Probably not adding some epsilon
(1) and (2) mean that there will be Z-fighting between the shadow map and the back faces.
Also, the shadow map resolution is not going to help you - just look at the wall in the shadow map, it's one pixel thick.
Recommendations:
Epsilons. Make sure that Z > lightZ + epsilon
Epsilons. Make sure that the wall is facing the light (dot of normal > epsilon) to make sure the wall is shadowed if it's very nearly orthogonal
I'm currently drawing a 3D solar system and I'm trying to draw the path of the orbits of the planets. The calculated data is correct in 3D space but when I go towards Pluto, the orbit line shakes all over the place until the camera has come to a complete stop. I don't think this is unique to this particular planet but given the distance the camera has to travel I think its more visible at this range.
I suspect its something to do with the frustum but I've been plugging values into each of the components and I can't seem to find a solution. To see anything I'm having to use very small numbers (E-5 magnitude) for the planet and nearby orbit points but then up to E+2 magnitude for the further regions (maybe I need to draw it twice with different frustums?)
Any help greatly appreciated...
Thanks all for answering but my solution to this was to draw it with the same matrices that were drawing the planet since it wasn't bouncing around as well. So the solution really is to code better really, sorry.