Lesson 7 : Mantra Render Engines
What I learnt in this lesson :
u Mantra Render engines and how it goes through the rendering pipeline
u Render at command line (save as .IFD)
u Mantra
u Rendering pipeline
u Instancing
u Bump and Shader
Houdini Command Line-j to call how many process will be dedicated to houdini
The command line “-j 3” mean I will use 3 process just for houdini
Extra info :
In order to ensure that the render will not take all the cpu, I can apply the same “-j” method for the rendering part.
Under the out, under the mantra's parameter there are many pre-build commands that we can use.
If choose “use one cpu” it will show mantra -j 1. Here I can change how many processor I want houdini to use to render.
Under the command file there is a disk file and I can save out my renders as .ifd format
What is ifd.?
Combination of h-script and binary data
In simple terms, it is for mantra to produce rendered image.
Rendering scenes using command lines
under the command line I can type cd (drag the file where you save your render image)
press Enter and type ls and enter again, it shows you the folder and files that is inside your project folder.
Then type “mantra < (name of render image.ifd) and it will start rendering the scene.
I tried applied the same method on to my command line but apparently it did not work.
Do I need to turn on disk file when I do external renders from the command lines? As disk file does not work on apprentice version.
Houdini website itself offers masterclass for mantra rendering.
Viewport vs Rendering Speed
In order not to slow down the viewport, I can click on the object and under render< geometry tab.
By ticking this, it allows us to see our geo high when it is rendered.
Refinement
it takes every faces of geo and render from one point to another depending on light and shader
eg) it takes from one vertex to another and smooth it by subdiving and makes new shade from one to a new one and if it cant, then it will keep subdividing.
If lets say we have a lot of geo in our scene and we have to instance geo then houdini has to refine all of the geo individually and that will take up render time. In order to be more efficient I could just refine the geo by using the subdive node before I instance and in that way, it will render most faster as it already been pre-define
Increasing shading quality
under mantra node < dicing, there is a shading quality parameter.
The higher the value, the refine your polygons are.
To be more productive when doing work, always ensure that if objects are more futher away from the camera, the obj can afford to have a slightly low divisions.
Bump Maps
Using bump maps will faster render time significantly
One way to add bump maps is to just use the mantra surface node and under its displacement tab < bump|normal map and I can use that to add bumps.
Another way is to use material shader builder and use the displace along normals node and tick the check box “bump only”
If using bump map avoid subdividing geo.
Properties affecting refinement
u Geometry measuring
Non-uniform : Measuring everything through camera spaceRaster – Screen SpaceUniform Measuring : Generating uniform division and the size of it control by the shading quality.
Buckets
I can render a greater “bucket” when rendering by increasing tile size
Coving
Some areas in geo need to refine more to get a smooth shading, and we might get holes in rendering and coving will help mend all back.
Opacity
Materials which are opaque and transparent (Of) on the surface geo will get calculated,anything further will be further down the pipeline.
Shading
When using PBR, arealight make a faster render and better image result.
Pixel sampling
The higher the pixel value, it has a better edge when render. The jitter will throw samples and random distances and getting a little smudge to get a cleaner lookHowever only if the geo has a lot of noises frequency, increase the pixel sample to get a smoother look.
First half of lesson
Lesson 8 : Mantra Procedurals
rest node - enable the texture to stick on to the geometry when the geo surface move/deformed
instance node :
under the instance node, there is this node called the point instancing node. In this, we have 3 options, "off", "full point instancing" and "first point instancing"
When use option "off" it is basically just duplicating objects
when use option "full point instancing" that is when point instancing occurs.
fast point instancing is the recommended choice as it is faster.
If i just want to render my instance and not the original geo, I can off the renderable on my original geometry.
I can create an instance tab on my geo and save it as presets to be more efficient.
we could also instance points from a geo and place another geo.
However, if we have a lot of geometry, it will slow down the machine. After instancing geometry on a point of another geometry, we could add a add point and under the point node there is an option called "delete geometry but keep the points"
When this is turned on, point can only be seen in 3d space but when render, we are able to see the geometry that we instanced.
Instancing is really an effective way to instance complex objects as point. By using the instance node, you will not be able to see the geo in 3d space but only when rendering.
This will allow the machine to be more fast and efficient if for example they are alot of high res geo to render.
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