Monday, January 9, 2017

San Miguel Scene

This post doesn't contain much technical content, because I was busy with moving to a new house and then the holidays, so I didn't have much time to write code. Instead, I'll post some images of the San Miguel scene modeled by Guillermo M. Leal Llaguno of EvoluciƩn Visual. I downloaded the Lightwave object file model and textures from the McGuire Computer Graphics Archive.

It took me a few days at an hour or so per day to get the scene to render correctly in 3DWorld. I had to add several minor new features, including a user-specified environment map cube, per-model normal map options, texture invert, custom sunlight intensity, custom mipmap creation for the leaves, and a per-material metalness parameter. Some of the features worked well, but others need more work. In addition, there are some errors in this version of the model, including missing triangles, missing textures, and incorrect texture coordinates. However, these problems don't affect the overall scene quality too much, as long as you're not looking at the details.

I computed indirect lighting for both the sky and sun for this scene using a preprocessing ray tracing operation that took around 10 minutes on 4 CPU cores. Once the preprocessing is finished, the lighting can be used for all view points and various weather conditions. There is no fake ambient term here, all indirect lighting is computed over a 3D grid. This isn't a closed model - meaning, many of the polygons are two sided and don't form a watertight volume. This leads to light leaking through the walls in some places. I don't have a good solution for this problem yet.

I used a single 8192x8192 shadow map and a 6 face 1024x1024 cube map centered in the courtyard for environment reflections. 3DWorld computes the shadow map and cube map when the scene is loaded, and updates them dynamically when objects move or any lighting/environment parameters change. This update requires the scene to be drawn multiple times, but there aren't any dynamic objects enabled by default so this isn't a problem.

Here are some screenshots showing the San Miguel scene from various locations and directions. These are some of the most photorealistic images I've gotten from 3DWorld so far. It can render this scene at an average of almost 200 frames per second at 1920x1080 on my Geforce GTX 1070.

View of the San Miguel scene from the corner showing shadows and indirect lighting.

View from the trees looking down. The indirect lighting appears to soften the shadows.

San Miguel scene viewed from near the fountain with a low value of sun and sky indirect lighting but strong direct sunlight.

View from the upper balcony showing closeup of plants. The sky is cloudy, which makes indirect lighting stand out more.



Here are some screenshots showing cube map environment reflections on glass and metallic objects. The reflection and transmission model is physically based and uses true Fresnel equations. Reflections don't use per-object cube map centers yet, so they're not very accurate, but they still look pretty good. There are some alpha blending artifacts due to not sorting the faces for individual objects from back to front. The materials are themselves sorted correctly as the viewpoint changes. Some of the objects are misaligned with each other, such as the salt shaker. This appears to be a problem in the model file and not a 3DWorld bug.

Reflections in glasses and silverware. For some reason, the salt shaker's salt, glass case, and metal lid are misaligned from each other.

More environment reflections of objects on the table.



Cube map reflection in the window. The reflection is a bit undersampled and distorted because it's far from the single cube map center point.

Cube map reflections in the silverware on a table. Can you spot the sun?

Here is a short video where I fly through the scene and examine some objects. At some point I'll have to add a system to improve the smoothness of camera movements when recording videos.


Here is another video with a slower camera speed and my attempt at smoother movement.



This work has been pretty fun and interesting. It's quite different from writing graphics and physics algorithms. I can't wait to find more large and interesting models like this one, and the museum scene from a previous post, to show in 3DWorld. If I find enough of them, I can combine them into some sort of town and maybe build a game into exploring the environments.

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