# 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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### Perspective transformation is perspective projection? [duplicate]

I know that ( Reference )in transformation source and destination has same coordinates dimensions. But in projection destination coordinate system has fewer dimensions than the source coordinate ...
1 vote
2k views

### Existence of vanishing point

Consider the following example of perspective projection: I have one railway track with two parallel lines meeting at the point $X$ at infinity which is the theoretical approach. This X is called the ...
1 vote
62 views

Shearing in $X$ axis is achieved by using the following shearing equations- $X_{new} = X_{old}, Y_{new} = Y_{old} + Sh_y × X_{old}, Z_{new} = Z_{old} + Sh_z × X_{old}.$ My question is during $Y_{new}... 3 votes 1 answer 652 views ### Difference between 2D and 3D pipeline 2D transformation and viewing: The camera projects the 2D world co-ordinate$(x_w, y_w)$on its projection plane which co-ordinates$(x_v, y_v)$. 3D transformation and viewing: The camera projects the ... 1 vote 2 answers 235 views ### Difference between perspective and parallel projection [closed] We know that in orthographic Projection Projectors (projection vectors) are perpendicular to the projection plane. And in Perspective Projection Object positions are transformed to the view plane ... 2 votes 1 answer 208 views ###$P^2\$ vs projection plane

I want to explain what I understood of definition of the two things. Projection plane: The general processing steps for modeling and converting a world coordinate description of a scene to device ...
1k views

### Calculating UV coordinates for sampling texture atlas

I have an 8192x8192 texture atlas that contains 1024x1024 shadow maps aligned side by side. I'm trying to calculate the uv coordinates so that I can sample each shadow map appropriately based on the '...
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1 vote
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### OpenGL transparency - object behind is not rendered

I'm trying to implement voxel world using OpenGL (Core 3.3). I've come across a problem with transparency. It looks like sometimes GPU decides to not render stuff that would be important. Can you help ...
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### Motivation behind tesselation

This question is NOT about the hardware difficulties and shortcomings of tesselation shaders I am trying to understand the motivation behind tesselation shaders. Why/when/where tesselation is a good ...
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### Is it possible that a superior, undiscovered 3D rendering method exists?

As far as I know, the only options we have for true 3D rendering are polygonal rendering, ray-marching and raytracing/casting. Why is that? Surely there must be other ways? Is there some paper ...
136 views

### Methods to interpolate between 2 topologically identical 3D meshes

I have 2 3D surface meshes. These meshes have vertex-correspondence and have the same topology (same edges and triangles connecting the vertices). However, the vertex positions (3d coordinates) are ...
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1 vote
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### Proprietary 3D Format Reverse Engineering: What Could These Numbers And Matrices Represent?

I'm trying to reverse engineer a model format from an older Russian game (Pathologic) with limited success. It is a proprietary model format not recognized by any converters/editing tools (believe me, ...
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1 vote
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### Why do OBJ files contain so many duplicate vertices if they use indices to define faces?

I have been experimenting with loading in OBJ files into memory using tinyobj. I have also been learning and analysing the OBJ file format specification. I have some code which loads the BMW car model ...
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### How to ensure that a randomly-generated velocity vector moves the camera forward within a valid arc?

I spawn a camera in a scene using random coordinates for x and y and setting z=0 and orient ...
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### How does 3D graphic software adjust for distortion inherent in perspective projection?

As this question and its answers point out, projecting a sphere on a flat picture plane, with perspective projection, may result in a ellipse, not a circle, and my understanding is that the only way a ...
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### Calculating the intersection of two volumes

What is an efficient way to calculate the volume of intersection of two arbitrary volumes described as closed surfaces? That is, with two meshes, A and B, how do I calculate the intersection of A and ...
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### How compute new camera parameters given a velocity vector?

My goal is to update camera parameters given a velocity vector so that the camera points in the direction of the velocity vector. How should one compute the update matrix for the camera parameters?
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### Convert point clouds into voxels

I have points that are obtained by sampling a mesh(which is not watertight). Now, I would like to convert that mesh into voxel? Does anyone have any suggestions for solving this problem?
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### Why do materials have both an ambient color and a diffuse color?

One of the first things I learned about computer graphics lighting (and light in general) is that when a ray of light hits a surface, the surface absorbs certain colors and the light retains the rest. ...
34 views

### Is there a Performance Penalty for LOD objects with different topology?

I have a fairly complex-shaped object I've modeled, and in creating the LOD meshes, I've merged some verts, deleted some and even added some after in cases where this manipulation produced an n-gon. ...
1 vote
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### How do I extrude a 2D Bezier curve representation into a 3D solid using Python?

Where P is the control point, w is weight. I plan to extrude this 2d representation into 3d. I have a discrete 2D representation (array which has [n_points, 2, 1] for each sample) of an airfoil that ...
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### How can I get a signed distance (SDF) from a mesh?

I am trying to use constructive solid geometry (CSG) and boolean operators to combine various shapes and get the outer (possibly concave) hull. This seems to work okay when using primitive shapes like ...
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1 vote
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### How to extrude a face from a selected mesh in Babylon,js using the ExtrudeShape method?

I'm trying to extrude a face from a selected mesh in Babylon.js using the ExtrudeShape but can't figure out why I got flipped faces. The bottom extrusions always comes flipped for a reason I ignore. ...
87 views

### UV coordinates calculation broken

I've tried using the classic formula of calculating barycentric coordinates. When the plane on which you are projecting the texture is collinear to any of the base vectors it crashes with a division ...
2k views

### How does OBJ format determine vertex normals?

I have a very simple obj file: ...
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### Under what conditions does a mesh operation cause the mesh become non-manifold and how to avoid it?

I'm implementing some mesh operations (e.g. edge collapse, edge split, edge flip etc) and need to ensure applying such operations does not cause the mesh to become non-manifold. However, I'm not sure ...
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1 vote
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### Plotting points along a 3D line segment

I'm trying to plot some points along a 3D line segment and could really use some help. In 2D, I've found success getting the angle of the line, the sine & cosine of the angle, and then adding the ...
843 views

### What software was used to make KDA - Villain?

I want to try making small clips with realistic environment with the lighting in the KDA music video... Any ideas what kind of program to use?
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### Calculating Material/Texture Placement from Bitmap to 3D Model

everyone! I am currently developing a program that converts a 3D model to 2D isometric pixel art. Part of my program extracts the texture from an FBX file (as FBX files can have textures built in), ...
389 views

### Why do some videos look smoother and others don't on the same monitor

I have a Dell monitor with 60 Hz refresh rate and therefore games playing on it are not very smooth as compared to 120 hz. But when I open videos on YouTube of the same game on the same monitor, some ...
189 views

### Mathematical Foundations of Radiative Transfer

I'm new to learning about ray tracing, but have been fairly confused by the mathematical foundations of it all. Specifically of radiometry/radiative transfer. I've internet searched a lot and skimmed ...
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### 3D Bouncing Cube

I'm trying to write a little program with a bouncing cube but I can't find the right x, y, z and angle for it. I have these lines: ...
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### Atmospheric scattering band/seperation artifact

I am currently experimenting with some atmospheric scattering in glsl in my OpenGL engine. I am experiencing a strange phenomena where a strange band / separation artifact appears along the middle of ...
1k views

### How are obj files textured?

I am a new learner in 3d graphics. So forgive me if I seem to ask something very basic. I am confused how obj files are textured. So far I have seen: obj + jpg obj + mtl + jpg When I look online, ...
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1 vote
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### Silhouette below 3D model

There are some 3D applications which can cast shadow or silhouette below 3D models. They render pretty fast and smooth. I wonder what kind of technology is the standard procedure to get 3D model ...
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I have the following .fx file for my shader: ...
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### What exactly is it about reality that is so difficult to recreate in a 3D simulation?

I have to admit that, while watching footage of the enhanced 2020 version of the 2018 game Forza Horizon 4, when they are driving fast, I have to sometimes remind myself that I am watching a video ...
69 views

### Algorithm to select regions based on curvature on a mesh

I'm trying to understand how to implement an algorithm similar to the one used by Magics' mark surface tool, you can see such behaviour on this video. Quoting the video: "Basically with this tool ...
1 vote
58 views

### projecting 3d onto 2d plane is not showing up correctly

I am trying to learn about 3d graphics from first principles, so i have decided to implement a simple thing, create a circle in 3d space & rotate it along some axis. I understand the basics theory....
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### Vertices, Vertex Normals and Face Normals

Using Open 3D Model Viewer, I have converted an OBJ file to an STL file. In the source file, the Vertex Normals are specified and in the destination, the face normal of the triangles are present which ...
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### Rounding a 3D corner with Subdivisions

Following the instructions from this post on Stack Overflow, I have been able to find points A, B, and C from points V1, V2, and V3 and a radius value (code below). I would like to be able to find a ...
514 views

### Blend Shape, Pose Blend Shape, and Shape Blend Shape

Since there is a lot of cross-section between computer vision and computer graphics for 3D pose and shape estimation of non-rigid objects, I would like to know what "blend shape", "pose ...
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1 vote
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### Real 3D interior room from 360 images

If I have 360 images of an interior room from all different angles, would it be possible with current 3D software technology to create a real 3D representation of that room, where the camera could ...
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857 views

### Detect collision for non axis-aligned bounding boxes

in my application, I needed to detect collision between 2 3D objects. To make it simple I can represent a object as a bounding box. So actually the task reduced to detect collision between 2 boxes in ...
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### How to decide which way to triangulate a quad?

Apologies if this is a dumb question... but given four arbitrary (non-coplanar) points in 3D space, there are obviously two different ways to triangulate the quad that they form. One triangulation may ...
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### How to Sample 3D Points Outside and Inside the Mesh Surface

I have a mesh of an object enclosed in unit volume cube and I would like to sample points inside and outside the mesh surface. What are the different ways of doing it? Is there any sample code ...
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### Is there a term for this sort of graphics?

I'd like to try to write some C code to create similar animated graphics to these, which are from a very old Commodore 64 game called "The Sentinel". I've been researching but I can't seem ...
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### Shear(?) matrix projection along Z (depth) axis

I'm creating a primarily 2d game (platformer perspective) with 2d background parallax layers. The parallax effect falls out of the fact that I'm positioning a bunch of layers in 3d and using a ...