Alex Turbosmooth Blog

Radiosity Tutorial

Alex "Turbosmooth Operator" — Fri, 26 Mar 2010 02:18:06 GMT

Radiosity.

In this tutorial, we'll attempt to mimic radiosity's lighting effect by manual placement of lights.

Radiosity has reached "buzz word" status over the years, but it is an important part of making the next step in scene lighting. It essentially mimics real-world light "bouncing" to produce much more realistic lighting by way of indirect illumination. Look throughout the room you're in now. You'll find significant portions of the room being lit indirectly, where there is no direct line of sight from a light source to the surface. This is accomplished due to the light indirectly bouncing around the room's surfaces to reach those spaces. You'll also notice that corners and creases receive less light due to the ambient occlusion.

Here is a quick video of what we'll outline in this tutorial.

(Please visit the site to view this media)

The tutorial starts off word heavy, but it gets less and less so as we go.

Please remember that every scene is different as is every lighting setup so this is only to guide the understanding rather than a strict rulebook. Also keep in mind that I am a simple artist who knows only the basics of light, there is tons of documentation for 100% accurate reproduction but you don't have to make it look perfect, only to the point where it looks "right". Feel free to mess around with it and don't be afraid to add your own style to it!

Note: Being that this involves adding quite a few lights considering the small scene space, deferred rendering would be suggested.

1. The basic scene. We've all seen a shot like this before, especially as dynamic shadowing engines have become more common place. There is one dominate light source and the portions of the scene not being directly lit by the main light rely on ambient lighting for their light source. The problem with this method is that the ambient light gives no distinctive shading or contrast to the different contours, materials and shapes. It looks flat, dark and unrealistic. Increasing the ambient light will not solve the issue as it will only rob more depth from the scene.

2. Here we've placed three point lights across the main light's hot spot on the floor. This is to simulate the light's bouncing off the surfaces such as the floor, ceiling and window edges as well. Note that these lights will obtain some color detail from the carpet as it would in the real world. To determine the color keep in mind the surface's material as well as the main light's intensity and color. For this the lights will have a pinkish color.

3. We use the same method for the other hot spot. Looking a lot better already.

4. Just as the floor causes the light to bounce so does the ceiling. To simulate this, we'll place our lights near the ceiling to both cast bounce light onto the floor but also onto the surrounding walls and ceiling. This doubles as light bouncing from the ground or objects outside up into the room.

5. A subtler touch is creating the light bleed from the windows themselves onto the ceiling. This can be an effect of the ground outside bouncing directly up, or the window sills/blinds doing the same.

6. In the next two steps we'll take the boxes into consideration. The boxes would bounce color and light just the same as the carpet and we'll try to mimic this. This step replicates the light bouncing off the boxes towards the ceiling with the lights being more intense and saturated where the sun light hits the box directly.

7. This step is an attempt to give the boxes some indirect lighting as well as giving a very small bit of yellow tint to their surroundings from that indirect lighting.

8. This final step is so subtle you likely wouldn't notice it, but it does bring the scene to its full depth. Three spotlights have been added to the scene to cast shadows, either individually or by shadow group, from the boxes giving them a sense of space in the scene. As with every step from four on, this is entirely optional.

Here is our final scene.

______________________________________________________________

Here is the scene we've created to first show this technique:

(Please visit the site to view this media)

And a screenshot of the difference:

If you have any questions feel free to ask in the forums!

Thanks!

Scene concepts in SunBurn

Alex "Turbosmooth Operator" — Sat, 19 Dec 2009 07:55:35 GMT

With our recent launch of SunBurn Framework complete I had some time to do what I enjoy most (mess around with SunBurn!)

I like to do quick scene "sketches" to determine how a certain art style and focus will come across in engine. Here's a glimpse into my thought process regarding how I came up with the lighting and materials of the scene.

First, we'll look at the scene without any textures on it. I use this method to get a rough lighting setup. This also demonstrates how little geometry definition you need to create a great looking scene with the tools SunBurn provides.

Applying materials (diffuse and normal with specular) really brings out the barrels. Giving the metal a much brighter specular emphasis really drives home the material definition.

For the floor texture, I went with a more "industrial" feel with metal grating. Why? Because it's awesome!

Let's do something with that wall.

Hmm, looks pretty bland. This is due to the lack of color variation in the lighting. Take a look at a few lights in your house or apartment, each one will likely give off a different tint due to the type of bulbs, shades or colors around it. This is what gives a scene depth.

Let's add a orange glowing light above the top barrel to mimic a glowing lantern (though I didn't get around to modeling it yet). Making it a shadow caster will add a lot to the scene.

Looks good, but the main directional light is killing it's effectiveness a bit. So let's disable that.

Much more atmospheric, but much too dark. It also has the same problem as before with having too little color variation. Two accent lights will help liven the room, but let's have two lights of opposing tints to help really bring something to the scene. I've added light orange and light blue point lights to opposite corners of the room. giving a very nice feel to the scene.

The lighting hues look fantastic, but the overall lighting effect looks flat due to the lack of shadows. John will hate when I do this, but let's add some shadow casters.

Here I've added two shadow casters in close proximity to the accent lights. Due to the simplicity of the scene, this hasn't really caused any performance concerns (still over 60 FPS on a 8800GT with heavy AA enabled).

I call this one finished for now.

Thanks for reading!

Alex

A glimpse into SunBurn examples.. (The Dojo)

Alex "Turbosmooth Operator" — Sat, 05 Dec 2009 06:03:47 GMT

The Dojo

We still have much to do, but it is coming along nicely after a day's work. Still many additions to be made and tweaks to be done, but we'd like for you, the community, to get a sneak peek at a future release! This example started out as an idea to show off the inverted green channel normal map trick (which inverts the lighting information to a face -- helpful for things such as tree canopies) but in the end that implementation wouldn't benefit the scene. We decided to go with a modular design allowing easy assembly of assets for a quickly constructed scene in our forward rendering solution.

Currently has one shadow caster (shadow group) and a handful of lights with HDR enabled.

Things to be done:

Corners!
Specular and diffuse maps changes or additions
Normal maps on various materials
Details (metal brackets, bolts, murals, candles, etc)
Lighting tweaks

Enough talk! Here's some screenshots, in SunBurn:

Thanks for reading! We look forward to see what you guys are working on.

Alex

Detail Maps and Basic Instanced Rocks

Alex "Turbosmooth Operator" — Fri, 09 Oct 2009 06:24:33 GMT

Hey all,

We've recently done some testing involving the use of two normal maps on objects, one to give an objects overall shape and form while the other gives a tiled detail map. To put it simply, we use two UV channels -- the first is a tiled UV map used for the diffuse and normal map for the material (ex: rock, sand, etc) and the second is a UV map with unique UV space for the normal map baked from a high res source to give the object's shape. This will give an object a non-tiled look from long and moderate distances but will give a very detailed look when up close due to the tiling of the material map.

We've had this idea floating around the office for quite a few months now. The basic idea is simple, but the implementation hit a few snags. Using two tangent space normal maps would cause additional tangent information stored in the vertex stream. Baking down both the detail map and shape normal map into a single tangent space normal map would require a large resolution texture (1024 or larger).

The solution we've chosen was using object space normal maps for the object form. This made our shader heavier, but it seemed the lesser of the three evils especially with a lot of objects in the scene at once since having a lot of vertex data or extremely large maps could cause much greater performance issues.

Here's a step by step example of what we're going for..

1. This is the basic low-poly object without any texture maps applied. Not too pretty, eh? It's a about 1.4k polygons for reference sake.

2. This is the low-poly with the object space normal map applied. It was created from a high-poly to low-poly bakedown.

3. This is our object with both the object space normal map and now the tangent space normal map applied to help define the material's detail. Notice how it's much more high frequency in detail.

4. As you can see the ambient occlusion map being applied here really brings depth to the rock. For more on creating ambient occlusion maps, click here.

5. Here's the final texture, the diffuse map. It gives our rock the color variation and any non-lighting oriented detail.

These are just some of the things we're working on here. I'd love to see what you guys are working on!

Ambient Occlusion Mapping Tutorial

Alex "Turbosmooth Operator" — Sat, 26 Sep 2009 01:04:00 GMT

Hey everyone!

Today we've finally rolled out our long-overdue Ambient Occlusion tutorial. We've designed it with the SunBurn community in mind using nothing more than XSI Mod Tool, a free program, and SunBurn. The basic idea behind the generation of the AO maps can be used in almost any modeling application as well as other free programs -- XNormal for example.

Problems and Solutions

In the making of this tutorial I ran into some snags here and there. The first biggest issue was XSI Mod Tool's FBX exporter seemed to remove any and all smoothing on meshes. The way around this was using the .XSI format. This solution opened up an opportunity for John to write up a very helpful XSI integration tutorial which can be found in step five of the AO tutorial.

How you can expand on this tutorial

This tutorial is a very basic example of how you can bake AO maps from a single basic mesh. Most of the same methods can be used with baking a high poly mesh to a low poly -- all except the portion of Step 3 involving the cloning of the low poly to be used as a high poly source. This is also meant to be used as a quick learning experience, so it contains using automatic UV unwrapping instead of the preferred method of manually unwrapping. This would be a necessity in more mesh-dense scenes. The better the UV mapping, the less seams you'll have, though they can always be manually edited later in a graphics editing program.

Screenshots

Here's the eyecandy.. (NOTE: the first image has no dynamic lights).