Breakdown Example

This week I finished a breakdown example for my class. I wanted to convince my students that working on breakdowns can be as exciting as working on the effect itself.

Here is the video:

Matte Painting Breakdown from Denny Iskandar on Vimeo.

Reflection on Batman Tumbler - Part 2: Reflection Color

In the previous post, we saw how I got back reflections and hit another problem with bump effect as shown here.

Figure 1. The last render we covered. Notice the bump effect problem on the metal piece near the back wheel.

There is a metal piece near the back wheel that should be smooth but looks bumpy. I checked the Bump map slots and found that the Bump map slot was assigned an incorrect bitmap. Easy to fix. Other than that, I felt the bump was too strong, so I reduced the bump amount from the default 0.3 to 0.15. I got this render.

Figure 2. Bump effect fix. Note that the metal piece near the back wheel now looks smooth.

At this point, the render looked fine and I could have stopped. However, I thought I should make use of the painted texture maps in some way. To begin, I assigned the Specular bitmap to the Reflection Color map slot.

Figure 3. The Specular bitmap

I know that reflection color for an Arch & Design material should be close to white. How do I make the Specular bitmap, which is rather black, close to white? I needed to cheat and I cheated in 2 steps.

First, I forced the image to be interpreted as if it had gamma value of 1.0 even though it actually had sRGB gamma (which is approximately gamma 2.2).

Figure 4. Forcing gamma 1.0 interpretation

Next, I manipulated the Output Curve of the bitmap to make it even closer to white.

Figure 5. Manipulating bitmap Output Curve

Here is a comparison to show what these steps do.

Figure 6. Specular bitmap comparison. 1: original image; 2: forcing gamma 1.0 interpretation; 3: manipulating Output Curve

With these manipulations, I got this render.

Figure 7. Render with manipulated Specular bitmap

Note that I got back the dirt details painted in the Specular bitmap. However, I found the reflection color of the dirt too dark. I know that the Diffuse bitmap has color for dirt areas, so I made another cheat: I added the Diffuse map, interpreted as having gamma 1.0, to the Specular bitmap. I used a Composite map to do this. Here is my setup.

Figure 8. Adding Diffuse bitmap to Specular bitmap

And here is the render that I got.

Figure 9. Render with Diffuse map added to reflection color

Now it is time to check the render from other angles.We will cover this in the next post.

Credit: The Tumbler model and textures were created by Henry Chan.

Reflection on Batman Tumbler - Part 1: Getting Back Reflection

Last week I did a quick Arch & Design shader test for my class. Here is the result:

First, a proper credit. The Tumbler model and textures were created by Henry Chan, a modeling student here at CG Protege.

The reason I carried out the test out was that Julien Lew, a student in the Visual Effects class I am teaching, used the model in his assignment. He worked on the shaders and could not get reflections on the model. In this post, I will share what I found.

Technical details are due. All the images were rendered using 3ds Max 2011, Mental Ray renderer. The shaders are Arch & Design.

I started off with this render.

Figure 1. Starting render. Note the lack of reflection on the body.

I used Mental Ray Daylight system and turned on the mr Photographic Exposure Control. I set Exposure Value (EV) to 10.0. To save effort of selecting a HDR map, I simply used mr Physical Sky map. I used a Photometric light for rim lighting and 8 photometric lights surrounding the Tumbler as fill lights. This way, I can get reasonably good-looking render without using Final Gather. Figure 2 shows my lighting setup.

Figure 2. Lighting setup

The first step in troubleshooting a complex shader is to understand its structure. Next, go through the structure to isolate the cause of the problem. Thanks to Julien's work, we isolated the cause of lack of reflections to the material called "Grey" assigned to the Tumbler body.

Figure 3. "Grey" material

The Reflection Glossiness map slot (highlighted in figure 3) caught my eye. Inspecting the bitmap used as glossiness map, I found that it was very dark.

Figure 4. Bitmap used as glossiness map

To verify, I rendered with the glossiness map disabled (in other words, Reflection Glossiness was constant at 0.5 throughout the surface).

Figure 5. Render with constant glossiness. Note the unnatural bumps on the metal piece near the back wheel.

Now I got reflections on the metal body. Problem solved.

However, another problem arose. One of the metal pieces near the back wheel had strange bumps (I expected it to be smooth). The next post will cover this.

Credit: The Tumbler model and textures were created by Henry Chan.