Questions tagged [rendering]

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44
votes
3answers
21k views

When is a compute shader more efficient than a pixel shader for image filtering?

Image filtering operations such as blurs, SSAO, bloom and so forth are usually done using pixel shaders and "gather" operations, where each pixel shader invocation issues a number of texture fetches ...
41
votes
4answers
25k views

Albedo vs Diffuse

Every time I think I understand the relationship between the two terms, I get more information that confuses me. I thought they were synonymous, but now I'm not sure. What is the difference between "...
29
votes
2answers
14k views

How can virtual texturing actually be efficient?

For reference, what I'm referring to is the "generic name" for the technique first(I believe) introduced with idTech 5's MegaTexture technology. See the video here for a quick glance on how it works. ...
29
votes
3answers
4k views

Avoiding z-fighting with coincident surfaces

When rendering two overlapping co-planar surfaces, a common issue is "z-fighting", where the renderer can't decide which of the two surfaces is closer to the camera, giving visual artifacts in the ...
19
votes
2answers
701 views

How do correlated samples influence the behavior of a Monte Carlo renderer?

Most descriptions of Monte Carlo rendering methods, such as path tracing or bidirectional path tracing, assume that samples are generated independently; that is, a standard random number generator is ...
18
votes
2answers
2k views

What is the “dipole approximation” for subsurface scattering?

If you read papers about subsurface scattering, you'll frequently come across references to something called the "dipole approximation". This term seems to go back to the paper A Practical Model for ...
16
votes
3answers
5k views

Difference between rendering in OpenGL and 3D animation software

With OpenGL and such I can render some pretty amazing looking things in "real time" 60 FPS. However, if I try to make a video of that same scene in let's say Maya, or 3ds Max it would take MUCH MUCH ...
15
votes
3answers
2k views

Importance Sampling of Environment Maps

What is the best currently known and ideally also production-verified approach for sampling environment maps (EM) in a MIS-based uni-directional path tracer and similar types of renderers? I would ...
14
votes
3answers
4k views

What are some methods to render transparency in OpenGL

Alpha blending can be turned on to make surfaces transparent, like so: ...
13
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4answers
3k views

For shader math, why should linear RGB keep the gamut of sRGB?

sRGB is often contrasted with "linear RGB." Images are stored on disk and passed to displays in sRGB, which is approximately perceptually uniform in intensity. Shader math is done in linear RGB, ...
13
votes
4answers
443 views

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

So I know that I'm basically asking to identify the main problem to be solved in creating realistic 3d Graphics, but as someone without much technical experience in the field, I'm curious that if ...
13
votes
3answers
3k views

Correct Specular Term of the Cook-Torrance / Torrance-Sparrow Model

For a while I have been doing some research on the topic of Physically Based Rendering. One reflection model that is mentioned over and over is the Cook-Torrance / Torrance-Sparrow model. It seems ...
11
votes
2answers
4k views

Physically based rendering and ray tracing

I've got a lot of confusion and I need to clarify some terminology and put together the knowledge. If I say that an engine is a ray tracer (so it uses the ray tracing algorithm to render the scene), ...
11
votes
2answers
2k views

What kind of technology would be involved in the rendering of human nails?

There are many references related to the physically-based rendering of several natural features of the numan body, such as skin, hair, eyes. However, I could not find specific information about the ...
11
votes
1answer
680 views

Compensation for energy loss in single-scattering microfacet BSDF models

Single-scattering microfacet-based surface models like the original Torrance-Sparrow BRDF or derived models like the BSDF for rough dielectric surfaces by Walter et al. neglect inter-reflection of ...
11
votes
1answer
4k views

Loop performance in a shader

I am wondering what's the best way to integrate a dynamic loop function in a shader? First, it seems that dynamic arrays are not possible. So, is it better to create a maximum size array and only ...
11
votes
1answer
502 views

Ocean Wave Rendering

How could I generate the waves for a water body with whitecaps & foam and variable intensity of the waves? Is the surface a mesh with a normal map? Is there a formula for generating that? Is there ...
11
votes
0answers
627 views

How correct is rendering in XYZ / linear RGB space?

I have a spectral power distribution (SPD, 5 nm steps) for all light sources in the scene and SPDs for the reflectance of all surfaces under any light / viewer angle in question. I'm going to ...
10
votes
3answers
2k views

Why do Vertex Buffer Objects improve performance?

From my basic understanding, a Vertex Buffer Object works something like this (pseudo code): Normally, if one wanted to say, draw a square, one could issue line drawing commands. ...
10
votes
2answers
7k views

Cause of shadow acne

I know how shadow mapping works but I am not getting the cause of shadow acne! Can anyone tell me cause of shadow acne in a simple way and how is it related to depth map resolution?
10
votes
2answers
270 views

Why for perfect reflections a surface must have G2 continuity?

Why for perfect reflections a surface must have G2 continuity (class A surface)? I would like a mathematical answer.
10
votes
1answer
2k views

Efficient rendering with many light sources

To render a scene with a single light source using phong shading, one can calculate the final color of each fragment passed into the fragment shader based on the ambient/diffuse/specular components of ...
9
votes
2answers
2k views

Rendering equation - why unsolvable directly?

Why is the rendering equation, introduced by Kajiya in 1986, not solvable directly/analytically?
9
votes
2answers
1k views

Fundamentally, how are 2D bitmaps rendered?

Suppose we have a 64-bit word-addressable computer and we want to program it to output a 5x7 character stored as a binary image bitmap (such as the one below) to a memory-mapped display. Since we ...
9
votes
1answer
719 views

Trying to implement Microfacet BRDF but my result images are wrong

I am trying to implement microfacet BRDF model. I am reading Sebastien Lagarde's slides. I implemented formulas to my code but i think result image is wrong. Yellow is base color of material. ...
9
votes
3answers
801 views

What are the usages of software rasterization in modern game engines?

I am taking a Computer Graphics course this quarter. One of our lab project is about software rasterization. Now I am planing the project proposal and thinking about how to make it useful for other ...
9
votes
0answers
210 views

Help with start up bias in Metropolis Light Transport

I'm trying to implement metropolis light transport based on this paper, and I have the basic thing working. I run the algorithm multiple times with different starting points, add the results for each ...
8
votes
1answer
463 views

How does the rendering equation incorporate shadowing

This is how the rendering equation is written in the textbook $$L(p,\omega) = L_e(p,\omega) + \int f(p,\omega_i,\omega) \, L(p*,-\omega_i)\cos \theta \, d\omega_i$$ which component of this equation ...
8
votes
2answers
171 views

Are vertices reprocessed per-poly for indexed meshes?

I've been digging a bit into what actually happens at a hardware level on the GPU, and found NVidia's Life of a triangle which explains the pipeline pretty well, at least for green boxes. One thing I ...
8
votes
2answers
621 views

Can (and how so) shaders paint screen pixels beyond those that occupied by the shaded mesh?

I have some experience programming geometry and compute shaders - but never adventured myself in really playing with the fragment shaders. Currently, I am trying to better understand how they work and ...
8
votes
1answer
3k views

Perspective Correct Texture Mapping

So I'm trying to correctly map my textures in my software renderer using the u, v coordinates but I can't seem to get it working. I got affine texture mapping working. This is what I can produce using ...
8
votes
1answer
780 views

How should I fill a shape consisting of Bezier curves and straight lines?

I have been working on a graphics library for some time now and have gotten to the point where I have to draw Bezier and line based fonts. Up to this point I am stuck with this: The green lines are ...
8
votes
1answer
2k views

What is “Object Space Lighting”?

Looking at Star Swarm, a demo for the Nitrous engine, I found this little line: "Nitrous uses Object Space Lighting, the same techniques used in film, including real-time film-quality motion blur." I ...
8
votes
2answers
925 views

What is a good approach for handling uniforms in modern OpenGL?

I'm creating a renderer using modern OpenGL (3.1 and up) and now I'm trying to create an efficient but flexible way of handling uniforms. I've been reading up on uniform buffer objects and on what a '...
8
votes
1answer
187 views

searching for acceptable quality shadow mapping techniques

Recently while searching of solving the shadow acne problem of traditional shadow mapping I implemented exponential shadow maps. It did the trick (no acne at all) but at the same time introduced other ...
7
votes
2answers
7k views

How to achieve gimbal lock with Euler angles?

I was studying about Euler angles and I came across the problem gimbal lock which can occur by using Euler angles. In gimbal lock we lose one axis of rotation. But how? And when does it happen? On ...
7
votes
2answers
234 views

What methods/technologies to reduce required performance for virtual reality are there?

I'm interested in virtual reality, but according to some sources, less than 1% of computers in use today have the necessary performance to run modern VR games, granted many of them are not intended ...
7
votes
3answers
463 views

Ambient Lighting

On the Wikipedia page for the Phong model, it says that the ambient term is a constant, and just gets added on to the other terms. But on other pages like LearnOpenGL it says you should take the ...
7
votes
2answers
604 views

How to handle a parametric equation in raytracing?

After taking a look at the Mobius strip, I noticed its equation is really simple and tried to add it into my Raytracer. I tried a "naive" way by simply generating N...
7
votes
1answer
3k views

Does PBR incur a performance penalty by design?

I am wondering if the various PBR models used in modern game engines for real time are heavier in terms of computation, that more classic approaches to rendering. Worded differently, is PBR just a ...
7
votes
1answer
3k views

Area Lights in Path Tracing

I have been following the scratchapixel ray tracing tutorials online which have been great at explaining the theory behind everything & how to implement it. However, I reached the point where I ...
7
votes
2answers
640 views

Moires patterns despite using mipmaps

I am working on Silverlight app. I am trying to render floor covered with tiles. Although I am using mip maps I am still getting awful Moire patterns, when trying to render big area. What I am doing ...
7
votes
2answers
166 views

To what degree, if at all, can custom code be embedded in a PNG, GIF, or JPG?

Computer graphics files are in Windows rendered by components such as the Graphics Device Interface and Direct2D. Is it possible to create a graphic file that, besides displaying a graphic also ...
7
votes
1answer
264 views

Matching a virtual camera to a physical camera

Say I've got a photograph of a scene, and measurements for part of it (eg. a room where I know the dimensions of the walls). Assuming a rectilinear lens, how would I go about setting up a virtual ...
7
votes
1answer
181 views

Proper architecture for rendering history of streamed data (points)

Overview My program receives some data points (0-400 per sec). ...
7
votes
1answer
929 views

Resulting Probabilty Density in Path Tracer for paths using Next Event Estimation

I am trying to implement my own Gradient Domain Path Tracer by following the code of this guy who already implemented it: https://gist.github.com/BachiLi/4f5c6e5a4fef5773dab1 I already managed to ...
7
votes
1answer
1k views

Anisotropic GGX BRDF implementation. How is it related to isotropic GGX BRDF?

Introduction I am implementing anisotropic GGX BRDF and have encountered strange behaviour of my implementation. I thought that if I compare the microfacet distribution function I have with the one ...
7
votes
0answers
200 views

Supersampling HDR

I'm encountering some issues supersampling in HDR for an SDR result and was curious what the usual method for doing this is. Notice how pixelated the edge of the white sphere is. Here's how I render ...
7
votes
2answers
1k views

Eye Parallax Refraction

I am trying to implement the Parallax Refraction effect explained by Jorge Jimenez on this presentation: http://www.iryoku.com/downloads/Next-Generation-Character-Rendering-v6.pptx and I am facing ...
6
votes
2answers
1k views

Is there some kind of Bresenham algorithm or equivalent for scanline rendering a rotated ellipse?

Back in the day when you often had to write your own low level rendering algorithms we all used to learn the Bresenham algorithms for lines and circles. It was almost trivially easy to extend the ...

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