Introduction

IMPORTANT NOTE: All the renders for this tutorial have been corrected with a Gamma of 2.2.

In this tutorial. I will cover basic and not so basic light properties settings in A:M for ray-tracing renders.

Ray-tracing is an important part of the Photon Mapping algorithm so setting the lights right for raytracing should be the first step in setting up a scene for radiosity.

This tutorial will also serve as a starting point for the next tutorial which will use the same basic scene to setup a realistic radiosity render.

When I started this tutorial, I thought of using an already existing scene suitable for radiosity so that I would not have to spend time modeling a whole room. So I selected a scene readily available which is the Thanksgiving Diner scene modeled and choreographed by Cindy Grove who did a good job particularly with the food models. This scene can be found on http://www.hash.com/freemodels/. On this page, select the "Scenes" icon in the right pane and then download the first downloadable scene you will find on this page.

Decompress that in its folder and then download and decompress http://www.ypoart.com/tutorials/downloads/AddOns.zip in the same folder. The add-ons comprises a project file reorganized so that each model is in its separate file. There are a few models too for which surface attributes and materials had to be slightly modified. By placing all the models in separate files, it will allow me to post new choreographies and models to be included without posting entire choreographies.

In A:M, open the project "Thanksgiving Diner Ori.prj" project file and render.

The image at right is what you should get.

This scene was theatricaly lit. By this I mean that lights where placed and oriented in such a way to spotlight some important objects in the scene just like it is done in theater lighting. However, the goal of this series of tutorial is to explore realistic lighting. So let's just discard the theatrical lights from the scene and replace them with candle lights to illuminate the scene as if it was illuminated from the chandelier lights above the table.

• First save the choreography under a new name "Default Candles.cho".
• Then delete all lights from the choreography.
• Create a new bulb light in the models container.
• Drop 5 instances of this new light in the choreography and position each of them at the center of each chandelier bulbs.
• Set the light width to 15cm so that it just covers the chandelier bulb and leave all the other light properties at their default values.
• Set the options to "cast shadow" for the chandelier in the choreography to OFF.

It is better to do the last step in the choreograghy rather than on the model itself so that the model stays untouched for later possible reuse.

Rendering at this point will give you the image at right. This scene is obviously too bright. This is something we are going to take care of in the next part.

A note about removing "cast shadows" on the chandelier: It is a compromise thing. The chandelier shadows does not contributes much to this scene except trouble getting rid of the shadows. The chandelier model is so near the lights that it cast really ugly crisp shadows on the walls looking like mach bands. And if you set multi rays, you get bad cases of noise everywhere. In this case, the trouble of keeping the chandelier shadows outweighted by far the realism that its shadows would have provided. There are much more important factors that will eventually contribute to the realism of this scene.