Archive for January, 2015

Source from Sébastien Lagarde: https://seblagarde.wordpress.com/2014/04/14/dontnod-physically-based-rendering-chart-for-unreal-engine-4/

some data by Sophie Van de Velde, Laurent Harduin

Basically the brightness of the albedo should fall in a range of 50-243dontnodgraphicchartforunrealengine4


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source: http://sharktacos.com/Forums/misc.php?action=help&hid=30

This outlines the steps for turning your hair geo mesh into Maya nHair. The starting point is to have a model with proper edge loops that flow in the direction of the hair. Once this look is approved, the process involves generating guide curves from the geo and then creating hair from those guide curves. These guide curves can then be rigged with the character and exported to an Alembic cache for lighting.

Part I: Generate guide curves from geo

The following method assumes you are extracting the curves from a polygonal model. An alternate method would be to either build NURBS geo, or convert the polys to NURBS (converting it first to subdiv then the NURBS) and then extract isoparms from these with edit curves > offset (with the offset to 0).

  1. Select an edge loop and modify > convert > edge loops to curves. Repeat for each edge loop.
  2. Add more edge loops to get even spacing as needed and convert these to curves.
  3. Edit the curves so they flow nice, don’t kink, and don’t loop around at the tip.
  4. Rebuild the curves (I did uniform: 4 spans)
  5. Make sure all the curves direction are going the right way. If not reverse them
  6. Group the curves.
    Additional subgroups can be used for organizational purposes as needed


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Stylize attempt


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[Notes] ShaderFX


Preference -> display -> rendering engine -> dx11.
Viewport 2.0 option -> performance -> transparency algoritm -> depth peeling
Turn on texture and light showing for the viewport to show the shader

hypershade -> shaderfxshader->in its attribute page -> open ShaderFX to launch the shader tree window.

Advance mode: inside the shader tree window -> settings -> Toggle advanced mode

ShaderFx window: Right click on empty space can choose nodes

Green: float 1 value, scalar input
Yellow: float 2 values like XY, vector
Cyan: float 3 values usually colour RGB values
magenta: float 4 values colour RGBA
Black: output colour of the whole shader

Group: compound the selected nodes into a single node group. Usage: select the nodes to be compounded -> shaderFX window -> group -> create group.  To expose -> click on the small rectangle icon on the top right of the group node


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[Notes] Renderman/Reyes/RIS

Statistics XML File: output an xml file of all the render data

Render Option -> Advanced -> statistics -> point the statistic xml file to a location -> the file may view in web browsers

Rendering Threads: will use the full power of the hardware to render stuff faster.

RenderMan -> render -> increase rendering thread to 8 according to CPU power

Linear: Only if the preview style is using classic maya render view.  The renderman “It” will added it itself.
1. renderman -> render -> preview style -> display -> switch it to “It”
2. (only if maya render view its used) render option -> passes -> output pass -> the 2nd exposure value -> switch to 2.2 (leave it to 1.0 if “it” is set to default display)

RIS Linear: Need to add attribute to the input RGB textures inorder for it to take it correctly
1. go to each image node attribute page -> attribute -> add texture control
2. under extra renderman attribute -> check linearize sRGB

Anti-Aliasing shading rate: the lower the shading rate the sharper the edges (higher division under the pixel). Render option -> quality -> shading rate.  Note that value 0 will give error.  It will also effect the bump coverage.  The lower the shading rate its going to cover a broader area of the bump.

– Pixel Samples: the higher the number will put in more sampling inside, However it will get grainy all together for a blur effects like depth of field.
– Filter: use separable-catmull-rom will have a great impact for depth of field.
– motion factor: will force renderman to stick to its shading rate.  In normal scenario, further or blur render eg motion blur and DoF since the output is blurred, renderman will increase the shading rate for those area to speed renders up.  However if the object has bump/displacement, it’ll actually change the detail of its geometry. It’ll endup being flicker in render sequence.   To increase the motion factor so it’ll fix its shading rate and it won’t drop to a point it’ll effects the displacement/bump.(to be at most efficient, apply custom attribute of motion factor per object bases on object that has displacement/bump rather than globally set it from render settings)

DoF : just simply activate from the active camera

Aperture control: add bokeh effects on camera.  Select camera -> attribute -> renderman -> add aperture control


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Values from DONTNOD for UR4

Reflectance Range in sRGB value 0-255

Plastic: 55-64
Rusted Metal: 52
Water: 43
Ice: 41
Glass: 57
Gold: 255 226 155
Silver: 252 250 245
Aluminium: 245 246 246
Iron: 196 199 199
Copper: 250 208 192
Chromium: 140142141
Nickel: 168155134
Titanium: 138 126 144
Cobalt: 169 167 161
Platinum: 171 162 149

All metallic materials should not have any diffuse value.  Since refracted ray will be absorb by the material(energy transfered into heat).  If the type of metal has some sort of colour tint(gold).  The tinted colour should be put in the reflective/spec map. Good reflectance value for conductor(metallic) materials are 50%-100%

ps: more scientific term of materials visit: http://refractiveindex.info/


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