I am totally new to openscad.
I am trying to generate two overlapping polygons (2D). I would just like to observe the outlines of both shapes at the same time.
I have managed to generate two different shapes. Although the shapes overlap, the renderer appears to show the outline of the combined shape with the inner part is filled in with colour.
How might I achieve my goal if the shapes were simply two overlapping squares?
I would be glad to see your code to understand exactly what you're trying to describe.
In any case, you must know first that openscad have several rendering types:
the f5 one is the quicker and doesn't really calculates the final result, only its image on the screen (that's why you cannot export with it)
the f6 one which does all the calculation of the points of the mesh and then render it (that's what you do to export)
the debug ones that are similar to f5
I think f5 could be your solution but it will look a bit "glitchy" because of the superposition of the two shapes. The fact is that I don't think openscad is made for what you want to do because you can consider that all that you put in your script is in a big union() block so when you press f6 all the independent shapes are combined into one and I don't think there is a way to prevent that. I should add that I think that the 2D functions of openscad are probably made to be used with the extrude functions to make 3D volumes for which the overlapping doesn't have a lot of sense.
Related
I'm creating a puzzle game that generates random sized pieces with 2D meshes. The images contain transparent portions and sometimes a piece is completely transparent. I need to detect what percentage of a piece is transparent. One way I found to do this is to go pixel by pixel. I posted my solution to this HERE. However, this process adds a few seconds during loading which I'd like to avoid and I'm looking for other ideas
I've considered using the selection outline of a MeshCollider to somehow to get a surface area I can compare to the surface area of the mesh but everything I find is on the rendering of outline with specialized shaders. Does anyone have any ideas on to solve this?
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1) I guess you could add a PolygonCollider2D to your sprite and use its Path for the outline and calculation of the surface area. Not sure however if this will be faster.
PolygonCollider2D.GetPath:
A path is a cyclic sequence of line segments between points that define the outline of the Collider
Checking PolygonCollider2D.GetTotalPointCount or path length may be good enough to determine if the sprite is 'empty'.
Sprite.vertices, Sprite.triangles may also be helpful.
2) You could also improve performance of your first approach:
instead of calling GetPixel as you do now use GetPixels or GetPixels32 and loop through the array in one for loop.
Using GetPixels can be faster than calling GetPixel repeatedly, especially for large textures. In addition, GetPixels can access individual mipmap levels. For most textures, even faster is to use GetPixels32 which returns low precision color data without costly integer-to-float conversions.
check only every 2nd or nth pixel as it should be good enough for approximation
limit number of type casts
I'm making a chess piece (a bishop) and I am trying to make the top notch.
For this purpose, I made a new cube, resized it and put on the place to make the cut.
I want to make a cut using a modifier: Boolean, intersecting the two objects.
The problem I am facing is that while intersecting, the top UV Sphere that simulates the 'hat' of the bishop disappears.
What I did so far:
- Remove Doubles
- CTRL+J to join Bishop+Hat(UV Sphere) to make 1 component
Nothing helped and when trying to intersect, the UVSphere-hat disappears.
Why? How to solve?
Here is the bishop before modifier, with hat:
Here is the .blend file to catch the problem faster:
Thank you for your help :-)
The boolean modifier offers two different solvers that produce different results. You want the intersect operation with the carve solver. You also want to hide the cube that you are using for the intersection otherwise you won't see the hole that it has cut out.
Just to go straight to the point I'll add the reply here and select sambler's excellent answer as right.
In my case the Cube which was going to intersect with the bishop HAD NEGATIVE SCALE.
If you have similar problems, check if your objects scale/parameters have negative parameters
I'm creating my game with dynamicly generated terrain. It is very simple idea. There are always three parts of terrain: segment on which stands a player and two next to it. When the player is moving(always forward) to the next segment new one is generated and the last one is cut off. It works wit flat planes, but i don't know how to do it with more complex terrain. Should I just make it have the same edge from both sides(for creating assets I'm using blender)? Or is there any other option? Please note that I'm starting to make games with unity.
It depends on what you would like your terrain to look like. If you want to create the terrain pieces in something external, like Blender, then yes all those pieces will have to fit together seamlessly. But that is a lot of work as you will have to create a lot of pieces that fit together for the landscape to remain interesting.
I would suggest that you rather generate the terrain dynamically in Unity. You can create your own mesh using code. You start by creating an object (in code), and then generating vertex and triangle arrays to assign to the object, for it to have a visible and sensible mesh. You first create vertices at specific positions and then add triangles that consist of 3 vertices at a time. If you want a smooth look instead of a low poly look, you will reuse some vertices for the next triangle, which is a little trickier.
Once you have created your block's mesh, you can begin to change your code to specify how the height of the vertices could be changed, to give you interesting terrain. As long as the first vertices on your new block are at the same height (say y position) as the last vertices on your current block (assuming they have the same x and z positions), they will line up. That said, you could make it even simpler by not using separate blocks, but by rather updating your object mesh to add new vertices and triangles, so that you are creating a terrain that is just one part that changes, rather than have separate blocks.
There are many ways to create interesting terrain. One of the most often used functions to generate semi-random and interesting terrain, is Perlin Noise. Another is his more recent Simplex noise. Like most random generator functions, it has a seed value, which you can keep track of so that you can create interesting terrain AND get your block edges to line up, should you still want to use separate blocks rather than a single mesh which dynamically expands.
I am sure there are many tutorials online about noise functions for procedural landscape generation. Amit Patel's tutorials are good visual and interactive explanations, here is one of his tutorials about noise-based landscapes. Take a look at his other great tutorials as well. There will be many tutorials on dynamic mesh generation as well, just do a google search -- a quick look tells me that CatLikeCoding's Procedural Grid tutorial will probably be all you need.
A recent question here made me think of SceneKit again, and I remembered a problem I never solved.
My app displays antenna designs using SK. Most antennas use metal rods and mesh reflectors so I used SCNCylinder for the rods, SCNPlane for the reflector and SCNFloor for the ground. The whole thing took a couple of hours, and I'm utterly noob at 3D.
But some antennas use wires bent into arcs or helixes, and I punted here and made crappy segmented objects using several cylinders end-to-end. It looks ass-tastic.
Ideally I would like a single object that renders the arc or helix with a cylindrical cross section. Basically SCNTorus, but with a start and end angle. This post talks about using a UIBezierPath in SK, but it uses extrude to produce a ribbon-like shape. Is there a way to do something similar but with a cylinder cross section (like a partial SCNTorus)?
I know I can make a custom shape by creating the vertexes (and normals and such) but I'm hoping I missed a simpler solution.
An arc you can do with SCNShape. Start with the technique from my other answer to get an extruded, ribbon-like arc. You'll want to make sure that the part where your path traces back on itself is offset by a distance the same as your extrusion depth, so you end up with a shape that's square in cross section.
To make it circular in cross section, use the chamferProfile property — give it a path that's a quarter circle, and set the chamfer radius equal to half the extrusion depth, and the four quarter-circle chamfers will meet, forming a circular cross section.
A helix is another story. SCNShape takes a planar path — one that varies in only two dimensions — and extrudes it to make a three-dimensional solid. A helix is a path that varies in three dimensions to start with. SceneKit doesn't have anything that describes a shape in such terms, so there's no super simple answer here.
The shader modifier solution #HalMueller alludes to is interesting, but problematic. It's simple to use a modifier at the geometry entry point to make a simple bend — say, offset every y coordinate by some amount, even by an amount that's a function of why. But that's a one-dimensional transform, so you can't use it to wrap a wire around on itself. (It also changes the cross section.) And on top of that, shader modifiers happen on the GPU at render time, so their effects are an illusion: the "real" geometry in SceneKit's model is still a cylinder, so features like hit testing apply to that and not to the transformed geometry.
The best solution to making something like a helix is probably custom geometry — generating your own vertex data (SCNGeometrySource). The math for finding the set of points on a helix is pretty simple if you follow that shape's definition. To wrap a cross section around it, follow the Frenet formulas to create a local coordinate frame at each point on the helix. Then make an index buffer (SCNGeometryElement) to stitch all those points into a surface with triangles or tristrips. (Okay, that's a lot of hand-waving around a deep topic, but a full tutorial is too big for an SO answer. This should be enough of a breadcrumb to get started, though...)
Here are some starting points that might help.
One approach would be to use more cylinders and make them shorter. That's the same idea behind the various segmentCount properties on the SCNGeometry primitives. Can we see a screenshot of the current linked cylinders version?
If you increase the heightSegmentCount, you could use the approach outlined here: scenekit, how to bend an object.
I just took a look at SCNShape. I was thinking you could use a shader modifier to warp the extruded shape into a circular cross section. But SCNShape doesn't seem to expose a segment count property, which I think you'd need to create enough extrusion segments for a good look. The chamferRadius and chamferProfile properties look interesting. I wonder if you could use those to create an extrusion that looks good.
I am able to draw shapes using the UIBezierPath object. Now I want to identify different shapes drawn using this eg. Rectangle , Square , Triangle , Circle etc. Then next thing I want to do is that user should be able to select a particular shape and should be able to move the whole shape to different location on the screen. The actual requirement is even more complex , but If I could make this much then I can work out on the rest.
Any suggestion or links or points on how do I start with this is welcome . I am thinking of writing a separate view to handle every shape but not getting how do I do that..
Thank You all in advance !!
I recommend David Gelphman’s Programming with Quartz.
In his chapter “Drawing with Paths” he has a section on “Path Construction Primitives” which provides a crossroads:
If you use CGContextAddLineToPoint your user could make straight lines defined by known Cartesian points. You would use basic math to deduce the geometric shapes defined by those points.
If you use CGContextAddCurveToPoint your user could make curved lines defined by known points, and I’m pretty sure that those lines would run through the points, so you could still use basic math to determine at least an approximation of the types of shapes formed.
But if you use CGContextAddQuadCurveToPoint, the points define a framework outside of the drawn curve. You’d need more advanced math to determine the shapes formed by curves along tangents.
Gelphman also discusses “Path Utility Functions,” like getting a bounding box and checking whether a given point is inside the path.
As for moving the completed paths, I think you would use CGContextTranslateCTM.