Grass Generator (pov-ray)

Grass generator (POV-Ray)

Description

The MakeGrass macro (mgrass.zip) generates a square patch of grass of a given size and density. Each blade is independently created with its own length and curvature. The patches can then be assembled into a prairie.

The patch mesh can be saved as an include file for later use.

L'usine � Gaz-on (the Grass Factory) is a Java application inspired by MakeGrass, that exports mesh2 files and is able to cover height fields adaptively.

Download

makegrass.zip (0.01 Mb)

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Usage example

Idea

Make a 3D rendering of a panoramic scene with some 3D vector objects added (e.g., a building, a tower, etc). We use GRASS here to get all data into a unique coordinate system (esp. for the 3D vector objects which are usually not geocoded).

What's needed

You need a (detailed) elevation model (DEM), a color orthophoto to drape over, and geocoded 3D vector data, perhaps originating from CAD software.

Procedure

Preparation:

Create GRASS location if you don't have it already, for example in UTM projection (use Location wizard)
Import the elevation model (DEM, usually in GeoTIFF format, import with (use r.in.gdal)
Import the orthophoto (comes typically in separated R/G/B channels within one GeoTIFF file, import with (use r.in.gdal)
Combine the usually separated R/G/B channels into one single colorized orthophoto composite (r.composite). Do not forget to set the current region to one of the channels first using g.region.
Import the 3D vector data (typically in DXF format and typically not geocoded but in xyz-coordinates, use v.in.dxf)
Geocode the 3D vector data (using v.transform). A 4 points transform will be sufficient which rescales the x, y, and z coordinates from the CAD geometric space to the geographic space.

Test visualization within GRASS:

Make a test visualization with nviz): nviz elevation=my_dem color=my_ortho_rgb vector=my_building3d

Export into POV-Ray formats: If that's ok, then start to export the prepared geodata for POV-Ray:

Export elevation model with r.out.pov: r.out.pov map=my_dem tga=my_dem.tga

Export R/G/B orthophoto composite with r.out.pov: r.out.png in=my_ortho_rgb out=my_ortho_rgb.png

Export 3D vector objects with v.out.pov: v.out.pov input=my_building3d output=my_building3d.pov objmod="pigment { color red 0 green 1 blue 0 }"

Rendering with POV-ray:

Create POV-Ray rendering script (see here for examples), see above for script to easily calculate rough camera and sun position coordinates.

Render it, for example (1100x900 PNG file) with: povray +Ipovscript.pov +Opovview.png +D +P +W1100 +H900 +A0.5