Questions tagged [rendering]
Questions about the conversion of a 2D or 3D model to a photorealistic or non-photorealistic image.
372
questions
0
votes
0
answers
22
views
Partial Derivatives of Spherical Angles and Refracted Ray w.r.t Surface u,v
I am reading on "Specular Manifold Sampling" paper with the implementaion(for the simple case) here on Mitsuba at github. As part of the calculation it needs to compute
partial derivatives ...
- 720
1
vote
1
answer
45
views
Confusion regarding incident direction in render equation
I am studying from pbrt-v3 and the rendering equation has just been introduced as
$$
\underbrace{L_\mathrm{o}(\mathrm{p},\omega_\mathrm{o})}_\text{Outgoing radiance }=\underbrace{L_\mathrm{e}(\mathrm{...
- 111
1
vote
1
answer
31
views
Sampling scattering direction around directions other than the last ray direction
In a path tracer, if we want to sample a ray direction in scattering medium, we can use phase function sampling, which actually use the direction of the ray before sampling as a sort of anchor to ...
- 485
0
votes
0
answers
13
views
HTML Canvas not drawing
I'm working on a 3D Renderer with the canvas element and JS but currently the cube I made is not rendering. I currently have it set to just render a wireframe of the cube and am hoping to render the ...
2
votes
1
answer
69
views
White spots when rendering diffuse material with environment light
I am trying to implement a simple shader. A round ball object is rendered with uniform albedo and I noticed some strange white spots on the outputs.
I perform importance sampling with 512 light ...
- 121
1
vote
3
answers
115
views
How does higher draw distance strain the CPU?
I am looking at many games like Dead Island 2, Red Dead Redemption 2, and Minecraft and I see that while the render distance grows, the CPU load grows with it. Why could this be happening? Lack of ...
1
vote
0
answers
36
views
Is it possible to render to a octahedron texture directly?
I am considering using octahedron textures for environment mapping, opposed to sphere or cube mapping due to their low memory footprint and the quality they result in.
Is there a possibility to render ...
- 171
1
vote
1
answer
101
views
Importance sampling in a path tracer
So, I'm attempting to implement a monte carlo path tracer that uses the ggx brdf model. However, I'm rather confused about how to sample the light direction.
I know that theta and phi can be sampled ...
- 13
0
votes
0
answers
77
views
One-sample model Multiple Importance Sampling with balance heuristic
Recently I feel a bit confused about one-sample model MIS. One sample model MIS can be found here in Veach 1997. 9.2.4 The one-sample model, and this one-sample model is widely used in the opensource ...
- 485
0
votes
1
answer
53
views
Triangle Rasterization Shaking Issues
I am making a Software renderer, and I noticed that there is a screen shaking like effect happening. shown in the first video:
I tried doing filling without clipping against the small square, and the ...
- 3
0
votes
0
answers
43
views
When do we need Dx12 Descriptors to be contiguous?
In many tutorials and examples code of DirectX 12 we can find ways to manage descriptors by creating a few descriptor heaps and allocating manually descriptors inside of them
(e.g. in Mini Engine the <...
- 11
0
votes
1
answer
129
views
What does GGX stand for?
Many render engines implement the microfacet model for rendering surfaces that are rough, metallic, and/or transparent, a concept first published in "A Reflectance Model for Computer Graphics&...
0
votes
0
answers
59
views
How to design an ergonomic software rendering pipeline with painter's algorithm?
I wrote my software renderer with C++20 and the DirectX Math library.
The pipeline so far consists of these steps:
I use vertex buffers (...
- 1
1
vote
1
answer
45
views
What algorithm approximates a "hand sketched" look for rendering diagrams?
I see a number of applications where polygons, lines, splines, etc., are algorithmically given a "hand drawn" look. What algorithm or general approach is applicable for this?
As an example, ...
- 111
0
votes
1
answer
38
views
My projection matrix for OpenGL fails on non-symmetric boundaries
Assuming my viewing volume has x coordinates varies from l to r, and y varies from top to bottom, and finally z-axis varies n to f, I derived the following projection matrix:
...
- 3
0
votes
1
answer
90
views
With a light source at (0,2,0) and unit cube (from [-1,1]) using a given shading formula, how is the r,g,b for each surface calculated?
The above problem is from a past Computer Graphics exam.
I am particularly confused about the explanation given, firstly for the top and bottom planes (since the direction of normal for top plane ...
- 3
-1
votes
2
answers
112
views
Whats the best way to render (2D) parametric curves with uniform stroke width?
I want to create a rendering engine that mostly renders parametric curves on a 2d screen. As far as it seems, todays graphics are all dependent on vertices and matrices, so not sure where to start or ...
user19809
0
votes
0
answers
18
views
How does denoising factor into most render engines + practical question
I'm a student working on an experimental animation.
The animation has been selected to be screened at a festival, but they would like a resolution that is beyond what my single graphics card can ...
- 1
1
vote
0
answers
54
views
How does changes in vertex data work?
I have been learning computer graphics and for some time and can't seem to wrap my head around one concept. How to handle vertex data changes?
Ex. 1. I have a text rendering on a screen. And up on ...
- 11
2
votes
0
answers
31
views
Optimized 3D rendering using dots and/or line segments of different sizes in Scratch
I'm developing a 3D rendering engine in Scratch, which is a block-based visual programming language. It does not have any support for bitmap rendering, but there is a "pen" plugin that lets ...
5
votes
0
answers
54
views
Facetted look when using SampleBias
I am writing a simple material system for a game.
Each material can have a specular value (phong) that is translated into "smoothness" via environment map.
Similar to PBR, I compute a ...
- 171
1
vote
0
answers
44
views
How to display real time 3-D orthogonal vector rotations?
I'm an embedded developer here with very little experience in computer graphics. I'm currently working on a GUI that can display a calculated inertial solution at run time. I have hardware that can ...
0
votes
1
answer
56
views
Does OpenGL allocate on glBegin/glEnd?
You can enclose arbitrary amount of vertices within glBegin/glEnd statements. Does OpenGL limit the number of vertices you create or it allocates memory for more?
user19644
0
votes
0
answers
83
views
Loading Gltf model pbr texture produces insane results
I built a gltf-viewer on my own, but the functionality for loading glf was implemented by referencing gltf-viewer-tutorial, the result is not correct. Below is my ouput for ToyCar.gltf .
The ouput of ...
1
vote
1
answer
90
views
Can anyone summarize in simple terms, how PSSMLT/MLT algorithms work?
I understand backwards path tracing and bidirectional path tracing (BDPT). However I'm failing to understand how Metrpolis Light Transport methods are even remotely feasible to run.
My understanding ...
- 195
3
votes
2
answers
254
views
What is the difference between a "meshlet" and just a small mesh?
Obviously, conceptually, a meshlet is just a small mesh. But what is the reason for making the distinction then? I'm assuming it has to do with how they are implemented.
In a meshlet architecture, ...
- 195
0
votes
1
answer
94
views
How can I transform the circular blinn-phong specular into a square shaped highlight?
I am creating a custom shading model in Unreal Engine and I would like to create a square shaped specular highlight, without changing the shape of the light itself.
I tried following the approach ...
- 291
1
vote
1
answer
117
views
Path tracing: how to deal with ray hitting an emitter
I am writing my first path tracer and kind of feeling confused by some mechanisms. For example, when I trace a ray and the ray hits a area emitter, then how to determine the radiance of this direct ...
- 485
3
votes
2
answers
145
views
cosine term in rendering equation
Rendering equation's value can be estimated with Monte Carlo (Physically Based Rendering: Light Transport I: Surface Reflection):
$\begin{equation}
\begin{split}
L_o(p, \omega_o) &= \int_{S^2}f(p, ...
- 161
1
vote
0
answers
25
views
A fresh perspective confusion about a paragraph
I am trying to re-implement the paper "A fresh perspective"
In this paper there is one paragraph on secion 2 that reads:
Usually, $z_s = z$
is the depth value of the point $P$, unchanged by ...
- 1,656
1
vote
1
answer
75
views
Rendering equation integration variable change
I'm watching the TU Wien rendering lectures in the course we were presented with a rendering equation (first one on the screenshot) and then another, which results from a change of variables (if I ...
- 13
1
vote
0
answers
117
views
Calculation of reflection vector in Phong specular lighting
I wrote the following phong reflection model for ray tracing in Rust, but I am not sure about the calculation of a reflection vector for the specular reflection.
...
- 11
1
vote
0
answers
53
views
Inverting perspective projection doesn't yield frustum?
I have a cube with 8 vertices representing the $[-1,1]^3$ cube vulkan uses for device coordinates.
The perspective projection matrix takes a frustum and maps it onto this cube. It thus makes sense ...
- 1,656
0
votes
0
answers
88
views
PBRT: why normalize ray's direction
In PBRT Chapter Camera Model, when describing Camera::GenerateRay(), it writes
It is important that the direction component of the returned ray be normalized—many ...
- 161
0
votes
1
answer
83
views
OpenGL - How to increase view space coordinate range in X and Y axis
I'm trying to render some objects but apparently X and Y coordinates need to be really small in-order to get something on screen. See this example of 2 lines
The world space coordinates for these ...
- 2,383
1
vote
0
answers
58
views
Question about reconstruction filter in ray tracing?
Suppose we have an 512x512 image, then the value of pixel j should be $I_j = \int_{0}^{512} \int_{0}^{512} h_j(u,v)L(u,v) \,dudv$, where $h_j(u,v)$ is the filter function for pixel j, $L(u,v)$ is the ...
- 11
1
vote
0
answers
65
views
Imprecise TEXCOORD interpolation of a screen quad in DirectX
I was debugging with RenderDoc an issue on an app based on Directx11 and 12 that draw screen space quads to perform various baking steps. These baking steps just render a quad in clip space without ...
- 41
1
vote
1
answer
101
views
3D to view plane projection
I am trying to draw points of a 3D sphere onto my monitor as if I was looking out into space. Me, the viewer, is at (0, 0, 0). The plane of my monitor is at (x, y, 1) and I have a sphere out in ...
- 21
2
votes
1
answer
134
views
How to draw smoother lines and triangles?
I am currently creating my own 3D renderer. Here is a coloured cube created by the renderer.
I modelled cube using a set of coloured triangles. Notice extraneous lines from edges and they does not ...
- 167
1
vote
0
answers
39
views
How to visualize the outgoing directions sampled from BSDF?
I'm trying to find a way to visualize the outgoing directions sampled from BSDF.
More specifically, for a given incident direction, I can sample the outgoing directions, using 'BSDF sample', and I ...
- 57
0
votes
1
answer
138
views
Bump mapping WITH precomputed tangents?
Most bump mapping (meaning black and white height map) uses Tangents/Bitangents computed from Position using dFdx/y. And they also compute the offsets/derivatives of the height map using dFdx/y. The ...
- 51
2
votes
2
answers
192
views
Adding cos(θ) from rendering equation ruins the renderings
I'm following Ray Tracing The Rest of Your Life to implement a ray tracer, but the explains on math (mainly pdf part) got me confused so I followed Rendering Equation to understand the math behind. As ...
- 161
1
vote
1
answer
862
views
On modern GPUs, what hardware do vertex/pixel shaders have access to that compute shaders don't?
Suppose that someone implemented rendering for a video game using entirely GPGPU apis, like compute shaders or CUDA.
Would it be possible to achieve the same performance as standard graphics pipelines ...
- 113
1
vote
1
answer
64
views
How is the distribution of normals constructed from the distribution of slopes in 'Understanding the masking-shadowing function' paper?
Recently I'm reading Eric Heitz's paper 'Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs', in section 5, 5.2, the paper defines the distribution of slopes and then says the ...
- 57
1
vote
1
answer
63
views
Is the dichromatic model physically based?
lately I have been learning about photometry, and everywhere I look I see a BRDF written according to the "dichromatic model". Roughly speaking: $$\rho= \rho_D+\rho_S \cdot (...)$$
for some $...
- 113
0
votes
1
answer
137
views
Text rendering - weird outline when zoomed
I'm writing a simple text editor using Vulkan for rendering, and I'm seeing some strange outline around the rendered letters if I take a screenshot of the text and zoom in, which bothers me because I ...
- 141
1
vote
0
answers
319
views
Generating cheap perfect outlines for meshes in WebGL
I am tasked with creating an outline shader in WebGL (i'm using WASM/Emscripten, so an OpenGL solution will work too) for meshes that the user can upload into our software (be it .obj, .fbx, .3ds), ...
- 111
4
votes
3
answers
283
views
Student-friendly ray-triangle intersection
I'm teaching a computer graphics course, and would like to give my students a function for calculating ray-triangle intersections (not just the point of intersection, but also the uv coordinates ...
- 251
0
votes
1
answer
396
views
Why does my Dell laptop monitor give this weird color banding?
I've noticed some very obvious color banding on the screen of my Dell Precision 7750 laptop while watching video (same in every video program; VLC, built-in Windows video player, etc.) Not only does ...
- 101
1
vote
1
answer
303
views
Back face detection
Suppose I have one convex polyhedron, I need to detect back face. And $N=(A, B, C)$ is normal vector of polygon surface and vector $V$ in viewing direction. According to books formula and internet ...
- 191