Working with the Renderer

This topic discusses ways to perform rendering tasks using pymxs.

• Executing your render
• Rendering to an output file
• Using pre- and post-render scripts
• Rendering Settings and Dialogs
• Working with the viewport
  • Iterating through the list of viewports
  • Maximizing and zooming a viewport
  • Saving the active viewport graphics window as a bitmap

Executing your render

The render() function invokes the 3ds Max renderer, and takes many optional parameters to control the rendering independent of the current Render Settings Dialog settings.

By default this function returns an in-memory render as a bitmap value.

# this will display the render in a virtual file buffer window
bmp = pymxs.runtime.render(pos=pymxs.runtime.name('vfb_upper_left'))
# the bitmap can also be displayed later:
pymxs.runtime.display(bmp, caption='My Bitmap')

Rendering to an output file

The render() function can save the render to a file if the outputFile: parameter is specified.

For example, this function (from the render.py pymxs sample) saves the rendered output as a single-frame jpeg file to the system default #renderoutput directory, removing the current render if it exists:

def render():
    '''Render in the renderoutput directory.'''
    output_path = os.path.join(pymxs.runtime.getDir(pymxs.runtime.Name("renderoutput")), 'foo.jpg')
    if os.path.exists(output_path):
        os.remove(output_path)
    pymxs.runtime.render(outputFile=output_path)

Using pre- and post-render scripts

There are two mechanisms to register pre- and post-render scripts:

• set the globals preRendScript (string) and usePreRendScript (boolean), or postRendScript (string) and usePostRendScript (boolean), which correspond to the settings under Render Setup Dialog > Common Parameters > Scripts in the user interface. This mechanism only works when the user presses the render button in the UI, these scripts are not called when the pymxs.runtime.render() function is called.
• register a #preRender or #postRender callback. This script will be called when pymxs.runtime.render() is called.

An example of the latter mechanism:

mxs = pymxs.runtime

def myPreRenderCallback():
    print('PreRender Callback Called')

mxs.callbacks.removeScripts(id=mxs.Name('MyCallbacks'))    
mxs.callbacks.addScript(mxs.name('preRender'), myPreRenderCallback, id=mxs.name('MyCallbacks'))
# this will run the registered script first:
mxs.render()

Rendering Settings and Dialogs

You can change rendering settings using the pymxs.runtime.renderSceneDialog struct. Note that changes to render settings should be made with the dialog closed (which you can check with the renderSceneDialog.isOpen() function). See the "Render Scene Dialog" group of topics in the MAXScript Help for information about properties and functions in this struct.

The renderer assigned to each type of render target is held in the renderers struct. For example, by default, renderers.production is the scanline renderer:

>>> pymxs.runtime.renderers.production
<Default_Scanline_Renderer<Default_Scanline_Renderer:Default_Scanline_Renderer>>

The list of all available renderer classes is held in the rendererClass.classes list, and can be assigned to a render target:

>>> pymxs.runtime.renderers.current = pymxs.runtime.rendererClass.classes[5]()

Working with the viewport

The viewport struct exposes properties and methods for working with viewports.

Iterating through the list of viewports

You can use the viewport.numviews property to iterate through the available views. For example, to list the viewports and their current layout types:

mxs = pymxs.runtime
for v in range(1,mxs.viewport.numviews+1):
    viewtype = mxs.viewport.getType(index=v)
    print(f'index:{v} view type:{viewtype}')

Maximizing and zooming a viewport

The MAXScript command to maximize or minimize the current viewport is a "Max Command", in the form of:

max tool maximize

As noted in Calling 3ds Max Commands, Max commands are not directly callable in pymxs, so to invoke this command, use:

pymxs.runtime.execute('max tool maximize')

Setting the zoom level of the current viewport is exposed through the viewport.zoom() function, which takes a float value setting the zoom factor, where 2.0 zooms "out" two times, while 0.5 zooms "in" two times. If the viewport is in perspective mode, you can also use viewport.zoomPerspective().

To "zoom extents", once again a Max command is used:

max tool zoomextents
max tool zoomextents all

Saving the active viewport graphics window as a bitmap

The viewport.getViewportDib() function returns a snapshot of a viewport's window image as bitmap. If no additional parameters are provided, it returns a bitmap for the currently active viewport. It takes these optional parameters:

• index - specifies the index of the viewport to capture; the default is the currently active viewport
• viewPanelIndex - specifies the index of the view panel to capture; the default is the currently active view panel
• captureAlpha (boolean) - specifies whether to capture the Alpha channel as well (ARGB); the default is False
• gammaCorrect (boolean) - specifies whether gamma correction is performed; the default is True

For example:

my_bitmap = pymxs.runtime.viewport.getViewportDib(captureAlpha=True)
pymxs.runtime.display(my_bitmap)