Mental Ray Part 1 - Basic Settings | Tutorial
by cgfreak
Software: 3dsmax
Author: Neoscape
Website:
Tutorial by Neoscape Artist: Carlos Cristerna
In this tutorial, I will try to help you understand the complex world of the mental ray render engine. The tutorial is intended for people with a basic knowledge of 3DS Max. I encourage you to search online for a little history of the render engine and then you will be good to start this tutorial. The website with some great information is: http://www.mentalimages.com. We will go through the basic features of it and what anyone would need to know to create an architectural render.
Start by creating a simple scene with massing objects in place of your final geometry. Remember it has to be to scale in order for it to work properly. I’ve also included a simple scene that is used in Mental Ray Part 2 if you’d prefer to use that.
Apply white material (arch & design) with default settings to the override material slot.
Then you will create two lights:
#1 - Direct = Both with standard settings; orange color; set the desired angle
#2 - Sky Light = Blue color; any place on scene
For the example: Intensity/Color/Attenuation = ORANGE
On the indirect illumination tab:
- Final Gather = Preset set to “Draft”
- Caustics and Global Illumination = default settings
- Check all objects create & receive G.I. & caustics
Then you should render a test; adjust color of lights if desired.
Create all new materials with the arch & design templates. For the grass & stones, use a blank template and add a map to the diffuse color (all materials with standard settings). Next add an environment map (360° degree preferable “hyperfocal sky”). With the default settings for F.G./G.I., render a test.
Tip
For the water, use glass and play with the reflection curve.
You will then want to displace the grass. Use a cellular map on the displace slot for the grass material. If you render it with the default settings, it should look like this.
Tip
The surface you are displacing should have enough subdivisions to render the desired effect.
In this next step, tessellate the geometry so that it can be displaced.
Tip
Use the “Edit Poly” modifier to tessellate. This will be a trial & error process depending on the size of your geometry. Start with a few and go on as you need more.
This is the result of the tessellation. If you still need more subdivisions for the displacement, try playing with the displacement map size.
In the displacement map, we only decrease the size from 1 to 0.1; the rest of the settings are default.
We are going to leave the grass that way assuming that is the desired result. For the water, we do the same thing except we use a noise map in the displace slot:
- Again, we only play with the size of the noise (from 25 to 5)
- Remember the geometry needs to have subdivisions
Assuming that we like the lighting and materials (displace into account), we turn off F.G. & caustics to fine tune our G.I. solution.
Turn on G.I. and leave all the settings default. You will notice that there is not much of a G.I. effect if you render. So what you need to do is set the size of your photons to something you can see so that you get an idea of what is going on with your G.I. solution. I usually start at (12 inches = 1 foot). Render a test and you will get this, not what we want but good to know.
Tip
Turn off displacement on your materials to save time in tests.
We need a G.I. solution that covers our entire scene; it does not need to be perfect. Start by adding more photons per light (1) - trial and error, depending on the conditions of the scene. If you want your solution to be stronger, you can decrease the “decay” (2) from 2.0 to 1.95. This is very sensitive so make it a small change. If you like your solution but do not want to keep adjusting the “decay of light” (2), increase the G.I. multiplier to your needs (3). (1.5 works for me in this scene).
Tip
if you get the error message
that “no photons are being stored…,” remember to turn on (4) “All objects Generate & Receive GI & Caustics.”
Render the scene and you should get this. Now we have color bouncing around and covering our entire scene.
Now turn off G.I. and turn on caustics. If you render it, you will get the above which is not very good, but you get an idea of where we are at in the process. You can see that there is an effect in there that is just not right (1). We will use the same process we used to the G.I. in which we play with the size of the photons (2), the amount of them (3), and intensity (4).
Decrease the size of the photons (1). By doing that, you will have to increase the number of them by A LOT (2) so that we get a nice and soft result. In this case, we will leave it at 1,000,000 (trial and error). Make sure you enable “Refract light and generate Caustic effects” (3) in the “Advanced Transparency Options” on your water material. Render a test and it should look like the image.
Turn on G.I. and caustics and the displacement on both water and grass. Render a test. Now we have to play with the intensity of both items to get what we want (1).
Tip
I usually balance those numbers for them to add to two: (G.I. mult 1.3 + caustics .7 = 2)
If you like the solution, you can save it to a file so that it can be reused later on in subsequent renderings (2). Just turn on the “Read/Write File” option and choose a location to be saved and render the image so it gets saved. If you modify anything in your lighting and G.I. & caustics, delete your old photon map by hitting the “X” button next to the saved map (3) and re-render.
Tip
You do not need to render these images full size or full resolution to save the photon map.
Turn G.I. and caustics off; turn on final gather and use the material override (see step 1) to render everything white. This will give you an idea of what is in your scene (remember skylight only works with F.G. on). Now tweak the intensity and color of your lights to what you like.
Tip
Direct light 1.0 orange/yellow; skylight .55 light blue
Change the Preset of the “Final Gather” settings from “Draft” to “High” (1).
Tip
Use draft settings to tweak color and intensity of your lights. Once you like it, render it high.
If you feel your shadows are too strong and want more light on it, you can increase the number of times light (2) bounces on to your scene with “Diffuse Bounces”.
Turn off the material override and render your image (with “Enable Final Gather” on). It should look like the image above.
Tip
Another way to get more light from the Final Gather solution on your scene is to limit the distance the rays travel by specifying the falloff distance (1). Zero to 500 is usually a good start (the smaller the number, the lighter the shadows).
Now enable the following:
-Final Gather
-Global Illuminations (render a test here)
-Caustics
One last thing before you render your final image:
The Arch & Design materials come with an integrated “Ambient Occlusion.” This feature will add detail to your image. As objects get closer to each other, they “occlude themselves” meaning that they get less light so they get darker (1).
Samples : more means softer solution, so between 16 and 32 is good (2).
Max Distance : distance that the occlusion or dark area spreads out (3).
Make sure to have “Use AO as Detail Enhancement for GI/FG” on (4).
Now you have an image with G.I., F.G., caustics and displacement with various amounts of materials all mostly with Mental Ray default settings.
For your final render, also increase the “Samples per Pixel” values from the default [¼ - 4] to [1 – 16].
Final Render:
Scene File Download: mental_ray_tutorial_scene_files.zip (46.35MB)
Nice website!!