Getting Maya 3D Paint to work

Software:
Maya 2018

Steps needed for Maya 3D Paint to work:

  1. Set a project folder and save your scene.
    * If your painting into an existing texture you can skip this step.
  2. Make sure your model has UV coordinates.
  3. Make sure your model has a basic Lambert material.
    * If you’re using a different material/shader on your model,
    Temporarily switch to Lambert just for the texture painting operation,
    And connect the original shader with the painted texture map to the surface shader input of the shading group after you’re done painting.
  4. In the Rendering tab toolbar, Double-Click the 3D Paint tool button to activate 3D Paint and also open its tool settings window.
  5. Make sure the object is selected.
  6. In the 3D Paint Settings window, go to the File Textures part,
    Choose a material attribute to paint to.
    * this would usually be Color because we are using Lambert temporarily anyway.
  7. Click Assign/Edit Textures to open the Assign/Edit Textures dialog,
    Choose a resolution and a file format for the new texture,
    And than click Assign/Edit Textures button at the bottom of the Assign/Edit Textures dialog to create the new texture and close the dialog.
    * If you already connected an existing texture file to the Lambert shader’s Color input you can skip this step.
  8. Check Update on stroke and Save texture on stroke.
  9. Set the viewport to Textured display mode.
  10. Set paint brush settings.
  11. Click the 3D Paint tool button to activate it and paint on the model surface.

Untitled-1

Advertisements

Maya – Setting the V-Ray Sun direction according to location, date and time

Software:
Maya 2018 | V-Ray 3.6

To set the VRaySun photometric light source diretion according to the location in the world, the date and the time:

  1. Select the VRaySun parent node – ‘VRayGeoSun1Transform‘ and rotate it so its Z axis points to the architectural plan’s south.
  2. Select the VRaySun node – ‘VRayGeoSun1‘ and in its attributes un-check Manual Position.
    This will make the location / date / time parameters accessible.
  3. Set the GMT zone of you architectural project’s location in the world, the Date and time.
    * haven’t found how to set daylight saving time….

Untitled-1

Related:
V-Ray for Maya Physical Camera
V-Ray for Maya White Balance
Daylight system addon for Blender

Arnold for Maya – Transmission Scattering (Ray Traced SSS)

Software:
Maya 2018 | Arnold 5

Scatter

The Arnold Standard Surface Shader’s Transmission Scattering options can be used for simulating highly realistic volumetrically ray-traced sub-surface-scattering suitable for materials like wax, soap, milk etc.

While the Transmission Depth attribute controls volumetric light absorption within the object (fog), the Scatter attribute controls what percentage of the light will be scattered instead of absorbed, effectively creating the murky effect of semi-transparent materials.

Note that for the scattering effect to work Scatter must have a dominant percentage value, and the Depth attribute must generally be much lower (shallower) than what would create coloring without scattering, otherwise the object will continue to look transparent and lacking the internal substance that we want to simulate.

Also note that the Opaque attribute must be unchecked in the Arnold attributes of the object’s shape node for the light to be able to pass into the mesh and illuminate the volume.
*This is actually a “cheat”, because physical semi-transparency has to be simulated by indirect light calculation or caustics, but for dense volumes like wax it’s very effective and the loss of realism is insignificant.

Untitled-1

Untitled-2.jpg

You can simulate the effect more accurately by rendering caustics,
In that case the Opaque attribute in the Arnold attributes of the object’s shape node must be checked and more steps must be taken allow refractive caustics to be ray-traced.

Note that simulating the effect using caustics will be very demanding in Transmission samples and Ray Depth.

Scatter_Caustics

Related:
Translucency

Using Arnold’s Ambient Occlusion node to create an eroding paint shader effect

Software:
Maya 2018 | Arnold 5

Arnold’s Ambient Occlusion (dirt) node can be used as a procedural mask to create interesting material effects like in this example of paint that is eroded at the model’s bulging areas to reveal metal beneath it.

In this shader’s case the Ambient Occlusion node is connected to the Mix property of an Arnold Mix shader, that blends between two different Arnold Standard Surface shaders, one simulating the underlying tin metal, and the other simulating the red paint that covers it.

Note that in the Ambient Occlusion node the Invert Normals property is checked, so that the effect will create a mask for the bulges and not for the creases,
And also that the Self Only property is checked so that the node will behave as a fixed object mask disregarding the proximity of other objects.
In this example the output of the Ambient Occlusion node is also process using a Remap Value node to increase it’s contrast so it will define borders between the areas.

Paint-Metal.jpeg

Untitled-1.jpg

Untitled-1

Maya Python scripting – Iterate through the timeline frames

Software:
Maya 2018

The following Python script iterates though Maya’s timeline frames, and for each frame creates a new cube, and aligns it’s position to the selected animated locator.

* There is probably a nicer way to set one object’s position according to anothers but haven’t found it yet (not finding enough examples of the cmds.xform command…) so sorry for that..

import maya.cmds as cmds

selection = cmds.ls(sl=1,sn=True)
for frame in range(1,80):
    cmds.currentTime(frame)
    newCube = cmds.ls (cmds.polyCube( sx=1, sy=1, sz=1), long=True)
    posX = cmds.getAttr(selection[0]+'.translateX')
    posY = cmds.getAttr(selection[0]+'.translateY')
    posZ = cmds.getAttr(selection[0]+'.translateZ')
    cmds.setAttr(newCube[0]+'.translateX',posX)
    cmds.setAttr(newCube[0]+'.translateY',posY)
    cmds.setAttr(newCube[0]+'.translateZ',posZ)

maya_python_frames

Maya Python scripting – Getting an object’s transform matrix relative to another object’s coordinates

Software:
Maya 2018

How to get an object transformation matrix relative to another object’s coordinates:
* The following script requires selecting 2 objects, the function will return the transform matrix of the first object relative to the transform matrix of the second.

from maya.api.OpenMaya import MVector, MMatrix, MPoint
import maya.cmds as cmds

def get_relative_transform (node,coordinate_space_node):
    node_matrix = MMatrix(cmds.xform(node, q=True, matrix=True, ws=True))
    parent_matrix = MMatrix(cmds.xform(coordinate_space_node, q=True, matrix=True, ws=True))
    return (node_matrix * parent_matrix.inverse())

node_a = (cmds.ls(sl=1,sn=True))[0]
node_b = (cmds.ls(sl=1,sn=True))[1]

print (get_relative_transform(node_a,node_b))

Untitled-1

V-Ray for Maya toon shading

Software:
Maya 2018 | V-Ray 3.6

Toon shading in V-Ray consists of two elements:

  1. A VRayToon node that creates a graphic contour effect on the rendered image.
  2. A flat shader that uses surface luminance data to define color areas.
    * A VRayLightMtl can be used for that.

Creating the VRayToon node:

  1. Click the Create V-Ray Toon button in the V-Ray toolbar to create a VRayToon node.
  2. In the VRayToon node attributes, set line thickness, color, and more graphic properties.
    * if you created a VRayToon node and it’s not selected RMB click the Create V-Ray Toon button in the V-Ray toolbar and choose Select VRayToon node.
    * To delete the VRayToon node, select it and press Delete.

Creating the toon shader:

  1. Create a VRayLightMTL node as the object’s surface shader.
  2. Create a Ramp texture node, connect it’s output color to the VRayLightMTL’s color input and delete it’s accompanying 2D placement node.
  3. Create a surfaceLuminance node and connect it’s output to the Ramp node’s V Coord input.
  4. Optional remapValue node between the surfaceLuminance node and the Ramp node to clamp the luminance values.
  5. Optional floatMath node to scale or manipulate the surfaceLuminance output value.

Untitled-1Untitled-2

Related:
Arnold for Maya Toon Shading