# Questions tagged [projections]

Questions about the conversions of a 3D model to a 2D model.

137 questions
Filter by
Sorted by
Tagged with
20 views

### Why does one matrix correctly project points to the plane, but another one doesn't?

I have a scene with a floating cube and a plane y=0. I want to create a simple planar shadow of the cube on the plane. To do this, I just have to project the vertices of the cube to the plane. I can ...
• 101
43 views

### Why does Zooming in does not work with Projection Matrix but works in Real Life?

My goal is to project 3D bounding boxes to an image. For those who are not familiar with what 3 Dimensional Bounding Boxes are, they are basically boxes defined by eight corners encapsulating an ...
25 views

### Ray direction in VR (Vision Pro)

I am trying to calculate the ray direction for each pixel in a post processing shader on the Vision Pro for raymarching. I am using the inverse of the projection matrix created from the tangents ...
• 101
41 views

### Ocean screen grid projection and animation

I am trying to port the Bruneton Ocean demo to Vulkan and I am having a bit of trouble with the coordinate system. I am using the matrices from the original code but I am not sure what this is doing: <...
31 views

### Name of non-standard perspective projection where parallel lines do not meet at a single vanishing point

I have made a non-standard perspective projection for a rectangular room (see left figure), in which for stylistic reasons, I chose to make the perspective "width" of the walls equal ...
38 views

### How are these two projection matrices related?

I have two 3D perspective projection matrices $A,B$ with standard projection parameters $k=\cot(\theta/2)$, where $\theta$ is the field of view, $n$ is the $z$-near value, $f$ is the $z$-far value, ...
• 157
1 vote
53 views

• 211
212 views

### OpenGL old-style diffuse shading producing unexpected effects

Question: What is going wrong with the shape of the contours of constant illumination in the below picture ? Detail: Although Lambertian shading might be ill-regarded because it exposes the hard edges ...
• 203
430 views

876 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 ...
334 views

### Parallel projection is special case of perspective projection

I synchronized with @David k's first and second answer regarding perspective and parallel projection. From the first question I understand that the image on the screen is typically described in ...
973 views

### Difference between transformation and projection? [closed]

We know that world coordinates $(x_w, y_w)$ transform to viewport coordinates $(x_v, y_v)$ which are the physical device coordinates. And during projection, any point $(x, y, z)$ projects to $(x, y)$ ...
1 vote
85 views

### Why shearing coefficients multiplying by y? [closed]

We know that shear is transformation that distorts the shape of the object. Shear relative to X-axis that is $y=0$ line can be written as: $x'=x+sh_x.y, y'=y$ My question is why $sh_x$ is multiplying ...
1 vote
312 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 ...
1 vote
1k views

### Why are vanishing point and centre of projection the same [closed]

We know that in perspective projection object positions are transformed to the view plane along lines that converge to the projection reference (center) point like this: But many websites say that COP(...
221 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 ...
1 vote
74 views

### What should be considered the origin of a ray used for object picking with perspective projection

I need to create a ray to pick objects in 3d environment using cursor. I'm not going to go into detailed math for this question. There's tons of information on that. In short terms, for orthogonal ...
• 516
352 views

### 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 ...
• 129
1 vote
642 views

### how to change the near clipping plane of a perspective projection matrix for OpenGL

I am trying to only change the near clipping plane of a given perspective projection matrix for OpenGL. My problem is, that the near clipping plane is way too close, and the far clipping plane is very ...
• 1,309
1 vote
163 views

### What is this graphical effect called?

I was watching this trailer: https://www.youtube.com/watch?v=pWh5388AEHw and at 1:22, the player used a magic trick that created a sphere that warped the projection of the scene. Does anyone know ...
• 113