generativepy.drawing3d module


Martin McBride, 2021-03-07
Tags drawing 3d drawing moderngl
Categories generativepy generative art

The generativepy.drawing3d module allows you to create 3d images using moderngl. It contains image creation functions, for creating PNG images, and frames.

make_3dimage

Used to create a single PNG image.

generativepy.drawing3d.make_3dimage(outfile, draw, width, height,
                                    background=Color(0), channels=3)
Parameter Type Description
outfile String The path and filename for the output PNG file. It should end in '.png'.
draw Function A drawing function object, see below.
width int The width of the image that will be created, in pixels.
height int The height of the image that will be created, in pixels.
background Color The background colour, defaults to black.
channels int The number of colour channels. 3 for RGB, 4 for RGBA

The channels parameter controls the transparency of the output file. To create PNGs with a transparent background, you should use RGBA.

Objects can be drawn with transparency even if RGB is used, but the image background will always be opaque unless RGBA is specified.

make_image creates a Pycairo surface and context, then calls the user supplied draw function to do the drawing.

The draw function must have the following signature:

draw(ctx, pixel_width, pixel_height, frame_no, frame_count)
Parameter Type Description
ctx Context A moderngl standalone context.
pixel_width int The width of the image in pixels. This is the same value as the width parameter in make_image.
pixel_height int The height of the image in pixels. This is the same value as the height parameter in make_image.
frame_no int The number of the current frame.
frame_count int The total number of frames.

frame_no and frame_count only apply to functions that create a sequence of images (such as make_3dimages below). The make_3dimage function only ever creates one image, so the frame_no will always be 0 and the frame_count will always be 1.

make_3dimages

Used to create a sequence of PNG images. These can be combined into an animated GIF or video.

generativepy.drawing3d.make_3dimages(outfile, draw, width, height, count,
                                     background=Color(0), channels=3)
Parameter Type Description
outfile String The path and base filename for the output PNG files. See below.
draw Function A drawing function object, see make_image.
width int The width of each image that will be created, in pixels.
height int The height of each image that will be created, in pixels.
count int The total number of images that will be created.
background Color The background colour, defaults to black.
channels int The number of colour channels. 3 for RGB, 4 for RGBA

The outfile parameter should be a base filepath. For example:

C:/temp/image

In this case the files will be created in the folder C:/temp, and their names will be based on the base name "image":

image00000000.png
image00000001.png
image00000002.png
etc

Once the images have been created, you can use an external program to convert them into an animated GIF or movie.

The draw function has the same signature as for make_image. In this case though, it will be called count times. The frame_count will always be set to count, and the frame_no will increment each time draw is called. You can use the frame_no value to draw a different image each time, to create animation.

make_3dimage_frame

Used to create a single frame.

generativepy.drawing3d.make_3dimage_frame(draw, width, height,
                                          background=Color(0), channels=3)
Parameter Type Description
draw Function A drawing function object, see below.
width int The width of the image that will be created, in pixels.
height int The height of the image that will be created, in pixels.
background Color The background colour, defaults to black.
channels int The number of colour channels. 3 for RGB, 4 for RGBA

This works in a similar way to make_3dimage, but instead of saving the image to a file, it returns a frame.

make_3dimage_frames

Used to create a sequence of frames.

generativepy.drawing3d.make_3dimage_frames(draw, width, height, count,
                                           background=Color(0), channels=3)
Parameter Type Description
draw Function A drawing function object, see make_image.
width int The width of each image that will be created, in pixels.
height int The height of each image that will be created, in pixels.
count int The total number of images that will be created.
background Color The background colour, defaults to black.
channels int The number of colour channels. 3 for RGB, 4 for RGBA

This works in a similar way to make_3dimages, but instead of saving the images to a set of files, it returns a lazy sequence of frames.

If you found this article useful, you might be interested in the book Computer Graphics in Python or other books by the same author.

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