Being curious about the character’s polygon count and texture maps, I decided to get some information about the game using PIX (Performance Investigator for DirectX), a tool that comes with the DirectX SDK. Using PIX, I ran the benchmark and when an interesting image appeared (shown in the screenshot below) I captured a Direct 3D frame, which contains all the API calls, data buffers (including vertices, textures and render targets) and shaders.

First I would like to say that every time I captured a Direct3D frame it came with thousands of API calls, making it difficult to find out where the interesting information really was. Also, I believe that because it is a benchmark the game is doing some repeated/unnecessary work. The following picture shows some of the rendering calls captured with PIX.

Next, I would like to investigate the rendering of the character who appears in the upper right part of the first picture. This character is draw inside the MultiScreenManager::Draw method as a set of parts/chunks. Note that in the previous picture the MultiScreenManager::Draw call was not expanded because it has lots of calls inside. The table below shows all the rendered parts/chunks of the investigated character.

As you can see, this character has almost 6K polygons divided into 10 chunks. All the chunks were drawn using an indexed triangle list with three DXT1 textures for diffuse color, normal map and specular map (or a mask, in some cases). I will not post any picture of the character textures but his face, for example, has three 128×256 textures.

The analyzed chunks have an average rate of one vertex per triangle, however, in a closed mesh with lots of triangles, each vertex is shared on average by 6 faces. Therefore, it might be possible to achieve a 0.5 vertex/triangle rate but I will leave this discussion for a future post.

The idea of his work, as I understand it, was to calculate the surface parametrization at the time the surface’s fragments are begin processed in the Pixel Shader. For that purpose, he uses ddx and ddy functions to differentiate the surface’s eye-space position received from the Vertex Shader inside each fragment processed. That way, for an arbitrary triangular mesh, he does not need to store the usual per-vertex UV, tangent or bitangent (also known as binormal) parametrization vectors.

One disadvantage of this technique is that it relies entirely on GPUs that support Shader Model 3 but I wonder if it would not be possible/viable to differentiate the surface in a deferred pass using the PS3 SPUs.

I implemented Mikkelsen’s Bump Mapping technique inside my old Detailed Surfaces Viewer project, making it easy for me to compare his technique with two others: Normal Mapping and Relief Mapping. My implementation differs from Mikkelsen because I still sample the surface’s height from a normal/height texture using an interpolated UV coordinate, and then use the ddx and ddy functions over it.

The first issue that I noticed in Mikkelsen technique was that I needed to scale the height map values to increase the normal displacement and make it looks like Normal Mapping. The following pictures show a flat surface rendered with Normal Mapping (left) and Relief Mapping (right) using the same normal/height RGBA texture/map.

The following pictures show the same flat surface rendered with Mikkelsen’s technique using the same normal/height texture. In these pictures the height values acquired from the normal/height texture were scaled using a different factor varying is ascending order between 1, 4, 16 and 32.

As you can see, the results obtained exhibits low displacement and low noise in the first pictures but better displacement and higher noise in the last ones. I would like to further analyze this noise issue to make sure I didn’t do anything wrong and to find out how to deal with it. Note that I’m using trilinear filtering here and that the height map is the same being used by the Relief Mapping technique.

The following pictures compare Mikkelsen’s Bump Mapping without parametrization (first line), Normal Mapping (second line) and Relief Mapping (third line) techniques using two other normal/height maps. Note that for the first technique a height scale factor of 16x was used for both maps.

I will update the Detailed Surfaces Viewer project as soon as I deal with the noise problem.

I was trying to update this website for a long time but after joining Tectoy Digital I could not find any free time to do that. Fortunately, I could find some time to work on this website again in the past weeks and after a lot of word it is finally ready! I tried to port all the content from my previous website to this new one but I decided to drop some old posts and projects leaving more space for the new stuff that is coming.

This new site was made using Wordpress and it has some features that I believe everyone will enjoy, such as commenting the posts or rating it. In the following weeks I will try to post some materials (projects and talks) that I worked in the past two years, as well as some interesting news. I hope you enjoy this new website!

Siggraph’s Student Volunteer is great program that provides students with a Full Conference Pass which allows you to go almost anywhere in the conference. As a volunteer you can apply for 18 or 30 hours of work, and if you apply for 30 hours you can also be awarded with housing. It was the second time that I applied for the volunteer program, and fortunately, I was accepted! =D

Are you attending to Siggraph this year? I would really like to meet you there. It will be my first time there and I would like to meet a lot of people.

It was the first time Imagine Cup featured a Game Development category, where students from all around the world competed creating a XNA games with the theme: “Imagine a world where technology enables a sustainable environment.”

Besides the Game Development category another brazilian team reached the forth place in the Software Design category. Check the Imagine Cup 2008 winners here.