Juan Carlos Moreno mentalray blog

A little fix

jcarlos — Sun, 06 Sep 2009 17:52:37 +0000

Thanks to Richard I saw that I had a dependency to a shader I wrote long time ago on the standalone mymr scene, I have removed it and it is now using only shaders that come on the original distribution. Please let me know if there’s any other issues

You can redownload the scene from here:
http://www.mymentalray.com/index.php?option=com_shaders&Itemid=107&Action=DisplayDetail&ObjectId=43

Thanks

Juan Carlos

A very simple scene

jcarlos — Tue, 01 Sep 2009 05:29:24 +0000

Below is the anatomy of a very simple scene completely completely step by step. You can download the file from here:

First we start with including the libraries we need. I am just going to use standard libraries.



link "base.so"

$include "base.mi"

Then we will include render options, notice that for now we are turning off pretty much everything except scanline rendering.



options "miDefaultOptions"

object space

contrast 0.1 0.1 0.1 0.1

samples -2 0

filter box 1. 1.

jitter 0.

samplelock on

scanline on

trace off

trace depth 1 1 2

shadow off

shadowmap off

caustic off

globillum off

finalgather off

geometry on

output on

end options

Next, we will create some objects and their instances. An object is an abstraction of the item, it will describe its properties and define the object. An instance will create the object and place it on 3d space. If you are familiar with Object Oriented programming, you will find them similar to Classes and Objects.

In the block instance you will notice a lot of weird numbers, for now ignore those. They are used to determine where in 3d space such object would live.

In the next block, I am going to create the lights and a light instance.



light "keyLightShape" "mib_light_spot" (

"color" 1 1 1,

)

origin 0. 0. 0.

direction 0. 0. -1.

spread 0.939693

end light

instance “keyLight” “keyLightShape”
transform
0.5 0.612372 -0.612372 -0.
2.77556e-17 0.707107 0.707107 -0.
0.866025 -0.353553 0.353553 -0.
0.0846911 1.17218 -24.3673 1.
end instance

Next I am going to create a camera.



camera "perspShape"

output "rgba" "jpg" "myRender.jpg"

resolution 640 480

aspect 1.33333

aperture 1.41732

frame 1 1.

clip 0.1 1000.

focal 1.37795

end camera

instance “persp” “perspShape”
transform
0.707107 -0.271035 0.6531 -0.
-0. 0.923623 0.383302 0.
-0.707107 -0.271035 0.6531 -0.
1.52933e-14 -0.908111 -10.8683 1.
end instance

Next I will create the materials that I will use with my geometry. Notice how it is calling the mib_illum_lambert (that is defined in base.mi) shader and assigns a red and a green color to its diffuse attribute.



material "red" "mib_illum_lambert"(

"diffuse" 1 0 0 ,

"mode" 4,

)

end material

material “green” “mib_illum_lambert”(
“diffuse” 0 1 0 ,
“mode” 4,
)
end material

Next I will generate the shapes that I am going to use, a sphere and a floor plane.



object "nurbsSphereShape"

visible on

basis "BSpline1" rational bspline 1

basis "BSpline3" rational bspline 3

group

# knot vectors

-9.18485e-17 -1. -3.36778e-16

-1.42767e-16 -1. -0.382683

-2.28978e-16 -0.783612 -1.17998

-2.20876e-16 1.13899e-16 -1.66001

-8.50305e-17 0.783612 -1.17998

4.09299e-17 1. -0.382683

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

0.382683 -1. -1.29648e-16

1.17998 -0.783612 -4.77031e-17

1.66001 1.22531e-17 1.01646e-16

1.17998 0.783612 1.92209e-16

0.382683 1. 1.76513e-16

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

9.17834e-17 -1. 0.382683

7.17729e-17 -0.783612 1.17998

-2.82324e-19 -8.93933e-17 1.66001

-7.21742e-17 0.783612 1.17998

-9.19136e-17 1. 0.382683

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

-0.382683 -1. 4.96700e-17

-1.17998 -0.783612 8.27423e-17

-1.66001 1.22531e-17 8.26519e-17

-1.17998 0.783612 3.47599e-17

-0.382683 1. -1.15624e-17

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

-1.42767e-16 -1. -0.382683

-2.28978e-16 -0.783612 -1.17998

-2.20876e-16 1.13899e-16 -1.66001

-8.50305e-17 0.783612 -1.17998

4.09299e-17 1. -0.382683

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

0.382683 -1. -1.29648e-16

1.17998 -0.783612 -4.77031e-17

1.66001 1.22531e-17 1.01646e-16

1.17998 0.783612 1.92209e-16

0.382683 1. 1.76513e-16

9.18485e-17 1. -1.79986e-16

-9.18485e-17 -1. -3.36778e-16

9.17834e-17 -1. 0.382683

7.17729e-17 -0.783612 1.17998

-2.82324e-19 -8.93933e-17 1.66001

-7.21742e-17 0.783612 1.17998

-9.19136e-17 1. 0.382683

9.18485e-17 1. -1.79986e-16

# texture vectors

0. 0. 0.

1. 0. 0.

0. 1. 0.

1. 1. 0.

# vertices

v 0

v 1

v 2

v 3

v 4

v 5

v 6

v 7

v 8

v 9

v 10

v 11

v 12

v 13

v 14

v 15

v 16

v 17

v 18

v 19

v 20

v 21

v 22

v 23

v 24

v 25

v 26

v 27

v 28

v 29

v 30

v 31

v 32

v 33

v 34

v 35

v 36

v 37

v 38

v 39

v 40

v 41

v 42

v 43

v 44

v 45

v 46

v 47

v 48

# texture vertices

v 49

v 50

v 51

v 52

# surface

surface "Surface" 0

"BSpline3" 0. 4.

0.

0.

0.

0.

1.

2.

3.

4.

4.

4.

4.

"BSpline3" 0. 4.

-2.

-2.

-1.

0.

1.

2.

3.

4.

5.

6.

6.

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

# texture surface

volume vector texture

"BSpline1"

0.

0.

4.

4.

"BSpline1"

0.

0.

4.

4.

49

50

51

52

approximate surface tree angle 10. 0 3 "Surface"

end group

end object

instance “nurbsSphere” “nurbsSphereShape”
caustic on
caustic 3
globillum on
globillum 3
material “red”
transform
1. -0. 0. -0.
-0. 1. -0. 0.
0. -0. 1. -0.
-0. -0.983205 -0. 1.
end instance

object “nurbsPlaneShape”
visible on
basis “BSpline1″ rational bspline 1
basis “BSpline3″ rational bspline 3
group
# knot vectors
-0.5 -3.06162e-17 0.5
-0.166667 -3.06162e-17 0.5
0.166667 -3.06162e-17 0.5
0.5 -3.06162e-17 0.5
-0.5 -1.02054e-17 0.166667
-0.166667 -1.02054e-17 0.166667
0.166667 -1.02054e-17 0.166667
0.5 -1.02054e-17 0.166667
-0.5 1.02054e-17 -0.166667
-0.166667 1.02054e-17 -0.166667
0.166667 1.02054e-17 -0.166667
0.5 1.02054e-17 -0.166667
-0.5 3.06162e-17 -0.5
-0.166667 3.06162e-17 -0.5
0.166667 3.06162e-17 -0.5
0.5 3.06162e-17 -0.5
# texture vectors
0. 0. 0.
1. 0. 0.
0. 1. 0.
1. 1. 0.
# vertices
v 0
v 1
v 2
v 3
v 4
v 5
v 6
v 7
v 8
v 9
v 10
v 11
v 12
v 13
v 14
v 15
# texture vertices
v 16
v 17
v 18
v 19
# surface
surface “Surface” 0
“BSpline3″ 0. 1.
0.
0.
0.
0.
1.
1.
1.
1.
“BSpline3″ 0. 1.
0.
0.
0.
0.
1.
1.
1.
1.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
# texture surface
volume vector texture
“BSpline1″
0.
0.
1.
1.
“BSpline1″
0.
0.
1.
1.
16
17
18
19
approximate surface tree angle 10. 0 3 “Surface”
end group
end object

instance “nurbsPlane” “nurbsPlaneShape”
caustic on
caustic 3
globillum on
globillum 3
material “green”
transform
0.0904705 -0. 0. -0.
-0. 0.0904705 -0. 0.
0. -0. 0.0904705 -0.
-0. 0. -0. 1.
end instance

Next we are going to put it all together by creating an instancegroup



instgroup ":world"

"keyLight"

"persp"

"nurbsPlane"

"nurbsSphere"

end instgroup

And finally, we want to tell mental ray how what we want to render



render ":world" "persp" "miDefaultOptions"

Notice that a lot of the options in the mi file are analog to the options available globally or per item in maya or 3ds max. For now I am going to let you try rendering this and you should be able to get a result similar to this:

First steps

jcarlos — Tue, 18 Aug 2009 05:54:45 +0000

Once we know we have a working version of mental ray, I think it is important that we know our tools.

What comes with mental ray standalone?

you should find 3 main directories:

bin – This contains mental ray and other useful tools
lib (or shaders) – This is the directory that mental ray, by default, will look for shaders libraries (so or dll files).
include (or mi_include) – This is the directory that mental ray, by default, will look for mi files. In some cases, the installation will also contain in this directory the header files for writing your own shaders.

Cool, but what are mi files?

mi files is the interface between mental ray and you. Actually, maya, 3d studio max and any other app that wants to interface with mental ray, converts internally their stuff to an mi file.

The mi scene files are quite complex because they describe the world, the geometry, materials, cameras, lights, shaders and options used in the scene.

For example, the following block describes a scene file with some default options, a camera and an instance of that camera in the scene:



options "miDefaultOptions"

object space

acceleration bsp

bsp size 10

bsp depth 40

task size 0

contrast 0.2 0.2 0.2 0.1

samples 0 2

filter mitchell 3. 3.

scanline off

trace on

trace depth 10 10 20

shadow on

caustic off

globillum off

finalgather off

lens on

output on

end options



camera "render_camShape"

output "rgb" "jpg" "myRender.jpg"

resolution 500 500

aspect 1.

aperture 0.94488

frame 1 1.

clip 0.01 1000.

focal 1.9685

end camera



instance "render_cam" "render_camShape"

transform

12.4929 -0.274935 0.318516 -0.

-2.64698e-17 9.46244 8.16776 0.

-0.420763 -8.16313 9.45708 -0.

0.957244 -8.17851 -69.2262 1.

end instance

…or the following block defines a shader description and the default values it will have



declare shader

color "MYMR_flat_color" (

color "color" default 1 1 1,

)

version 1

apply material

end declare

I promise that we will get into details of what each of these things mean but I won’t go too deep into mi files because it is a very wide topic that I can’t really cover in one single post.

Going back to what we got with mental ray, I would like to spend a couple of paragraphs describing the tools in the bin directory:

fg_copy – Final gather map utility (I will get back to this one when we cover final gather)
imf_copy – Image conversion tool, useful for converting file formats (for example: exr to jpg). Mostly used for map files which will accelerate the performance of mental ray.
imf_diff – Image comparison tool, useful for debugging images
imf_disp – Image display tool. Useful tool for displaying the renders on your monitor.
imf_info – Tool for displaying information about the image like resolution, bitdepth, gamma, colorspace, format, etc.
mkmishader – Tool for creating basic shader c code from a mi file.
ray – Renders an mi file using mental ray. also a metasl compiler
spmstat – Displays information about your licenses

Knowing the tools we have available, we will go tomorrow through our first scene setup.

Where to start? – mental ray 101

jcarlos — Fri, 14 Aug 2009 04:36:38 +0000

Where should I start?

Simple, in the begining!

Great, but… how do we define the begining?

For now, I am to remove the middle man (applications that wrap around mental ray) and will just work with just mental ray.

Why?

Because at the end of the day everything on any application (maya/3ds max) is translated into mental ray terms.

Ok, cool but what am I going to need?

A decent computer.
A copy of mental ray stand alone, which you can get if you get a copy of the book Writing mental ray shaders: A perceptual introduction by Andy Kopra
mymentalray.com standalone scene, which you can download here.
An account at mymentalray.com for posting questions at the forum and for downloading things that we learn.
Some basic command line knowledge
Patience, lots of patience, but you will be rewarded.

How do I install it?

I could write a bunch about the installation and tricks for each platform, but I am going to let you read through the PDFs. Be sure to request the license from mental images according to the installation.

Ok, It is installed, now what?

Lets start rendering!

Once you have downloaded our scene file,

Open a terminal
- Windows Start Menu: run -> cmd (enter)
- Linux (depends on your distribution)
- Mac OS X (Finder: Go – /Applications/Utilities/Terminal.app)
Go to the directory where the scene file is (usually on the Downloads directory if you used Safari or Firefox)
- Windows: cd c:\Documents and Settings\$username\Downloads
- Linux and Mac OS X: cd ~/Downloads
Go to the actual folder for the scene:
- All platforms: cd MYMR_material_standalone
Render it:
- All platforms: ray MYMR_Material_new_mi_export.mi

Your output should look like this:

First render using the standalone mymentalray.com scene

Ok, I am going to let you guys have a little bit of rest so that this info sits down and is absorbed.

This will be eventually some tutorials on mymental ray.com and I will appreciate feedback regarding any issues.

In the next post, I am going to give an overall explanation about a scene file and its contents.

Hello world!

jcarlos — Tue, 14 Jul 2009 05:59:12 +0000

Welcome to my mental ray blog, on this blog I’ll about mental ray stuff and other film-related/production stuff and how it relates to this wonderful software.

You might be wondering how is this going to be different from other mental ray blogs?

Let me be honest with you, I don’t want to “compete” with any one elses’ blog. I feel that the more information out there, the only one benefited will be the community. All I can promise to you, is that I will try to keep it simple, honest and interesting.

I will start from the very begining, there might be things that you know already or you have come up with your own techniques, or you have any suggestions of things that you’d like to see please contact me: jcarlos@mymentalray.com.

Thanks and I hope you enjoy it.

-Juan Carlos