Questions tagged [3d]

Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.

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After making any 3D model using Opengl how to export it's data in .dae file?

I'm trying to make simple 3d modeling program in c++ with Opengl. So I don't know how to transfer/convert/export or save data of 3D model in .dae file. NOTE:- 3d model is made using Opengl ...
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Intrinsic Matrix vs Perspective projection matrix

I was going through the camera matrix explained in the wikipedia article and understand how the matrix K \begin{bmatrix}f_x&s&x_0\\0&f_y&y_0\\0&0&1\end{bmatrix} is built. The ...
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43 views

Estimate 3D cube pose after camera rotation

I have some photos of 3D cube. I also know the 3D pose of the cube in each photo (yaw, pitch, roll). I want to estimate the new pose (yaw, pitch, roll) of the cube after performing 2D rotation to the ...
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1answer
38 views

Understanding the near clipping plane

I don't understand something about the near clipping plane. It's there to avoid the division by $0$ but when we compute the pixel coordinates, we just need to multiply by the clipping plane to clip ...
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58 views

BSP tree rendering

As a little project, I'd like to implement a BSP merging algorithm for Boolean operations on solids. But to even tell whether it works, I need some way to render the BSP tree. In other words, I have a ...
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2answers
137 views

What are “Triangles” in 3d modeling?

In 3d modeling, there is some "triangle count" which determines complexity. I am not sure but I think cubes have 12 triangles or somethong.But I see NONE They have squares, no triangles! Can someone ...
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1answer
69 views

How can I raycast with chunks?

I am attempting to implement chunks/octrees to speed up my render times. However, sometimes the walls show horizontal or vertical lines (rays hitting the inside of voxels?) or some blocks disappear ...
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1answer
51 views

Why is the z direction away from the screen/viewer?

I wonder what is the reason that when z increase, the objects appear far away and when z is negative, the object is behind the camera?
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2answers
59 views

Visualize the interpolated unit quaternion on the surface of the unit sphere

My major is mechanical, please forgive me for asking questions that may seem trivial to you. First, I'm reading the following paper: Dam, Erik B., Martin Koch, and Martin Lillholm. Quaternions, ...
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1answer
69 views

Compute Speed of Spheres in 3D animation

I have created two animations: One where a "camera" moves towards the spheres creating an optic flow (1st GIF).The code can be found here. One where spheres move randomly in a 3D coordinates space (...
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1answer
128 views

Rendering equation for spherical lights

I am currently implementing spherical lights in my DirectX game engine. I decided to build the shading formula from the classical rendering equation. Here is what I get: The simplifications show that ...
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19 views

Apply a pose to a 3D model/mesh

Assuming that I have pose information for a human, is there any ways/tools to apply that pose to a 3D model? Basically, given continous pose information say from a dancing person, I like to animate a ...
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1answer
36 views

Calculating normals for vertices which aren't a vertex of all neighbouring triangles

In my procedurally generated mesh in Unity, not all vertices are vertexes of all neighbouring triangles - essentially, it's a grid with cells of varying sizes. This is messing up the calculation of ...
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19 views

Is it possible to set visible and color for all 12 edges(spines) of the figure (cube) in matplotlib?

In 2d, matplotlib plots all 4 edges(spines) of a figure. In 3d, matplotlib plots 9 out of 12 edges of a cube. Is it possible to set visible and color for all 12 edges(spines) of a cube in 3d? I ...
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1answer
45 views

Why does my code generate a figure whose kurtosis looks a little higher than the one I am trying to reproduce?

this figure (fig_1) is an univariate normal distribution in 3D, the corresponding equation is in the top left hand corner it seems that x varies from -5 to 5; sigma varies from 0 to 4. This Python ...
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1answer
41 views

Why does my code to plot a cone actually generate a roof?

per this post, this formula $Z = 1 - \sqrt{X^{2} + Y^{2}}$ generates a cone where the point is at (0, 0, 1) and it spreads out below that. It meets the x-y plane at the unit circle I am trying to ...
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1answer
83 views

Could some give an explanation or hint about this kind of equation? $\left(- \sqrt{X^{2} + Y^{2}} + 1\right) \cos{\left (2 \pi X + \phi \right )}$

This is a screen shot from an animation generated by a matplotlib example the key part in the code is ...
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2answers
68 views

Creating a Smooth 3D Mesh from a 2D Outline

I am trying to find (or maybe create) an algorithm for creating a smooth, rounded 3D mesh given a 2D outline. I'm trying to recreate a system from a Gamecube game called Amazing Island, and you can ...
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1answer
256 views

What's the difference between Clipping and Culling?

In a tutorial about OpenGL both words are mentioned, unfortunately without a good explanation. To find out, I have read this article three times, but I fear I'm a too common man... my understanding is ...
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1answer
85 views

Calculating the angle between two polygons

For my application, I want to render models as polygonal surfaces in 3D space and have edges that are bent "outwards" to have a solid line and those who are bent "inwards" to have a dotted line. So if ...
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1answer
36 views

What is performance better - add four materials to mesh or duplicate every vertex and use packed texture?

I am making ski jumping game (in Unity) with procedurally generated hill mesh. I want to add lines on hill like this (mesh is created by script, but I've manually assigned materials in Blender) ...
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13 views

How can I detect if an edge has flipped during the UV unfold process?

I'm writing my own UV Unfold operation (similar to Maya's Optimize UV tool or 3DS Max's Relax Tool). My code works great 90% of the time but in some instances, I'm getting faces and edges that flip ...
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81 views

Help with understanding the look-at function (the view matrix)

I've been reading this article about the look-at function. I don't understand the part when they're trying to inverse the matrix N. They say that R is orthogonal because all its row and column ...
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2answers
338 views

How can i create a 3D Sphere(earth) using OpenGL, GLFW, GLAD, GLM?

Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can ...
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1answer
174 views

What are the i,j,k components of a 3d mesh on plot.ly (online)?

A 3d Mesh on plot.ly online graph maker (https://plot.ly/create/#/) takes 3 mandatory variables (X, Y, Z) and 3 optional variables (I, J, K). I understand that if I want to draw a cube that I then ...
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20 views

Newby - which computer language for video to video &/or 4-D to video

First post on forum. What's the simplest language / package for computer graphics that will do what i need? I have two projects in mind: One is to input a video (eg. from youtube) and process it ...
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86 views

Why don't I see tile-based 3D graphics?

As we know, tiles can make it quicker to update large portions of the display at once, as compared with a bitmap. To put, say a letter, on the screen, the Commodore 64 typically does two writes (the ...
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2answers
398 views

Programmatically generating bin files for GLTF models

I have a need to generate a series of GLB files. I have a base template for a GLTF file which I have to derive off of. The models thus generated will only have varying textures on them. The base mesh ...
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76 views

Using octree for cheking intersection of ray and meshes

I wrote the code for checking intersection of ray and meshes on scene. It consist of two parts - broad phase and narrow phase. In broad phase I build an oriented bounding box around each mesh and ...
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1answer
316 views

Vulkan: efficient way to update VBO mesh vertices?

I would like to change/add/remove some mesh vertices in existing VBO's (while deforming and remeshing 3D objects) . With OpenGL I would have to reload whole vertex VBO's. I suppose with Vulkan there ...
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67 views

Programmatic rendering of 3D animations

Many years ago I used POV-Ray to render some 3D animations. I liked POV-Ray's Scene Description Language (SDL) as I could generate the required files programmatically using other languages (e.g. Perl)...
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2answers
300 views

Unfold a 3D mesh to a 2D plane

I'm trying to unfold a 3D mesh onto a 2D plane. My general idea to do this, would be to cycle through all the faces of the meshes and perform a hierarchical transformation. So I would start at the ...
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1answer
129 views

Rendering 3-D point clouds obtained from depth maps as a 2.5D video

Suppose I have code to generate a bunch of frames, each of which is a depth map(I have access to the matrices which represent depth) which in turn is used to generate a point cloud. One frame would ...
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1answer
138 views

Why do animated CG characters always feel fake?

Why do animated CG characters always feel fake? Usually if a CG character is an animal (or humanoid creature), they tend too look kinda off. Their movement tends to look oddly smooth or lightweight, ...
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2answers
147 views

transformation from cartesian coordinates to spherical coordinates without calculations

Given this graph in the 3d cartesian coordinates i should figure out the spherical coordinates representation but without the use of calculations . I've been trying to solve this the whole day but i ...
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1answer
29 views

Can you generate your own HDRI maps without using photos?

For example, preparing a scene in Maya using standard lights and rendering out a panorama? Could they also be made from scratch in photoshop using 32bit color? Is there a reason why people don’t ...
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0answers
53 views

Intersecting Frusta

I am trying to determine whether two frusta intersect in 3D space and to quantify this intersection as a percentage of one frustum volume (eg. 100% intersection meaning that the two frusta occupy the ...
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1answer
69 views

If you can use subdivision surfaces for 2D curves

I've seen how subdivision surfaces are good for 3D curves/modeling, but haven't seen anything on if it's good, or even usable, in 2D. My question is just that, if (a) you can even use subdivision ...
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1answer
109 views

Problems with Subdivision Surfaces

It sounds like Subdivision Surfaces are better than NURBS but not as good as T-splines. I would like to know some of the disadvantages of Subdivision Surfaces, what they can't do or what they do ...
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40 views

Convex hull around polygon for cave mapping

For the purpose of mapping caves, we survey new passages so that we take main polygon (survey from point A to point B) and on each "node" (survey station A in example), we shoot multiple "splay shots" ...
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2answers
373 views

How to get the 3D position for the point with (0,0) UV coordinates?

I have a 3D triangular mesh(vertices, indices, uv coords) that I'm rendering to the screen. Let's assume that the UV mapping is one-to-one. I'm trying to find a way to find the 3D position of the ...
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1answer
47 views

Export Model Textures Per Face

(Note that as far as attempts go, I can't find anything that helps me) I have a 3D polygon, and for simplicity's sake it's going to be the one below: It is textured using the UV map below: Side ...
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2answers
423 views

3ds max: Z-fighting when working with Large Objects

I had a z-fighting/z-clipping issue with a scene containing some very large objects yesterday in 3ds max. It can be seen in the image below: For some reason downscaling the scene significantly (a ...
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1answer
228 views

Rendering Fluid Simulations?

I've read about Lagrangian and Eulerian fluid simulations and here's what I take from their methods: Lagrangian - Simulating fluid particles by calculating displacement for each particle Eulerian - ...
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1answer
88 views

Overlaying a grid on to a height map

What is the method used in overlaying a grid (agonostic of the grid type) on to a height map? It seems it's some sort of projection, but what are the technical details in how to implement it? An ...
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2answers
584 views

How can I draw this style of grid?

I'm trying to write code (in any language) to render this 3D grid, matching the look and colors as closely as possible:
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1answer
137 views

3D scene construction and change of coordinates

My book says: After a scene has been constructed we transfer object descriptions to the viewing-coordinate reference frame. This conversion of object descriptions is equivalent to a sequence of ...
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1answer
118 views

What is the equivalent of rotation matrix in Euler angle space for Quaternions?

I have to load a mesh in Blender (which uses Z and Y as up and forward axes), modify it and export it (with setting up and ...
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1answer
62 views

How to rotate a shape in another 3D software so that the rotation matches with the rotation in Blender?

I import a mesh in Blender, export it with setting axis_forward='-Z', axis_up='Y', import in NVIDIA's FleX, rotate it and store it on disk; I call this mesh ...
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1answer
82 views

How to compute A and B in projection matrix

I'm trying to compute a projection matrix to transform from view space to NDC with a near clip plane at -1 and far plane at +1. The general form of this matrix (disregarding aspect ratio and focal ...