Mars renderings using the 1/8 degree data

Written and rendered by Paul Bourke
October 2000

Original rendering

Zoom x 2

Zoom x 4

Mars, The Whole Planet

Written by Paul Bourke
July 2000

The following renderings were created using PovRay. They are based upon the 0.5 degree gridded datasets from MOLA (Mars Orbiter Laser Altimeter). This is one of the products in the MGS mission (Mars Global Surveyor). The mission was launched from Cape Canaveral, Florida, on November 7, 1996 and reached Mars on September 11, 1997.

It is a credit to PovRay that this model, which contains over half a million triangles renders in less than 5 minutes (600MHz Dec Alpha ev67). In order to further reduce rendering times for animation sequences, back face culling was performed before the scene was passed to PovRay for rendering. This typically reduced the rendering times for each frame to less than 2 minutes.
Input_File_Name=mars.pov Output_File_Name=mars.tga Output_to_File=on Buffer_Output=off Quality=9 Radiosity=off Output_File_Type=T Width=800 Height=600 Antialias=on Antialias_Threshold=0.1

This rendering is with a virtual satellite 10,000 km above the center of the planet. Given a radius of about 3,500 km, this amounts to 6,500 km above the surface. During the mapping stage of the MGS mission the real satellite orbited at, on average, 400 km above the surface. The mapping stage of the mission started in March 1999 and was expected to last for 1 Mars year, 687 Earth days.

The MOLA data is converted into PovRay triangles, each triangle having a precomputed colour definition. For technical reasons the triangles need to be enclosed within a "mesh {}" structure.

mesh { triangle { <,,> <,,> <,,> texture { Matxxx } } : : }

As with most terrain mapping the surface features are exaggerated in order to make them more noticeable. The first image on the right has a vertical height scaling of 5.

#declare marsfinish = finish { ambient 0.4 diffuse 1 specular 0.1 roughness .1 } #declare marsnormal = normal { bumps 0.5 scale 5000 }

All the remaining renderings use a height scaling factor of 30.

The great rift valley is a deep long crack in the surface, extending almost 5,000 km and 100 km wide in places.
The colour variation in height was created by mapping the following colour ramp between the lowest and highest elevations.

In total 2000 predefined materials were created from the colour ramp above, for example the first is:

#declare Matxxx = texture { pigment { color rgb <0.215686,0.215686,0.176471> } finish { marsfinish } normal { marsnormal } }

Mars has two moons, phobos and deimos. The orbit of phobos, the larger of the two moons is 9,378 km which is about the same distance as these renderings. Deimos is much further away with an orbital radius of 23,459 km.

camera { location <10000000,0,0> up y right 4*x/3 angle 60 sky <0,1,0> look_at <0,0,0> }

The tallest point on the surface is Olympus Mons which stands about 24 km high but with only 500 km diameter at the base, rising from a smooth plane. It is a shield volcano but unlike on Earth where plate motion tends to form strings of volcanoes, on Mars there is no plate motion and the volcanoes tend to rise up in a single location.

It is a straightforward matter to flood the planet to any arbitrary depth.

#declare seapigment = pigment { bozo turbulence 1 octaves 6 lambda 3 omega 0.5 color_map { [0.0 color rgbt <0,0,0.7,0> ] [1.0 color rgbt <0.5,0.5,1,0> ] } } sphere { <0,0,0>,1 pigment { seapigment } scale 3.35155e+06 }

The first image in this series has an additional cloud cover made up of carbon dioxide.

sphere { <0,0,0>, 1 pigment { bozo phase cloudphase turbulence 1 octaves 6 lambda 3 omega 0.5 color_map { [0.0 color rgbt <1,1,1,0.4> ] [0.5 color rgbt <1,1,1,1.0> ] [1.0 color rgbt <1,1,1,0.4> ] } } scale 3634943.61 rotate <0,cloudrotate,0> }

Data resolution

There isn't enough topological detail to get too close to the planet. At the equator, 0.5 degree sampling results in a resolution of around 30 km. The image on the right is a view at the equator looking east at a height of about 100 km above the surface, the facets are clearly visible.

One way of reducing the visual artefacts would be to calculate normals at the vertices and blend the colours across the facets. While this is common practice for many rendering applications it gives terrain models a false impression, landscapes tend to be fractal not smooth. The method employed here was to use spatial subdivision to generate geometric detail. The image on the right has had each facet divided into 4 and the introduced vertices randomly perturbed depending on the local height variation.

The example on the right has each facet subdivided into 16 smaller facets. The appearance of the facets has been mostly removed, most importantly the surface still looks like it has detail rather than becoming smooth. The disadvantage of course is that the geometric detail has increased significantly, view frustum culling was introduced in order to bring the polygon count down.

The moons

Phobos

light_source { <0,0,-4> White }
light_source { <0,4,0> White }
light_source { <4,0,0> White }

camera {
  location <2.5,0,0>
  look_at <0,0,0>
}

sphere {
   <0,0,0>, 1
   texture {
      pigment {
         image_map { gif "phobos.gif"
            map_type 1
         }
      }
   }
   scale <1,0.820895522,0.686567164>
        rotate <0,clock*360,0>
}

Deimos

light_source { <0,0,-4> White } light_source { <0,4,0> White } light_source { <4,0,0> White } camera { location <2.5,0,0> look_at <0,0,0> } sphere { <0,0,0>, 1 texture { pigment { image_map { gif "deimos.gif" map_type 1 } } } scale <1,0.813333333,0.693333333> rotate <0,clock*360,0> }

In July 2000 the 1/8 degree datasets were released. While this doesn't particularly alter quality of the renderings given above, the extra resolution does permit one to get closer to the surface before artefacts due to the polygonal faces becomes obvious. Here are some examples of a 2 and 4 times zoom. Note that this model has 360*8*180*8*2 or over 8 million triangular facets. After back face culling this reduced to just over 2 million.

Rendering of the North Pole of Mars

Written by Paul Bourke
September 1999

The data is sourced from the NASA Planetary Data Systems Geophysics Nodes as part of the MOLA Mars Orbiter Laser Altimeter project. An example of the data released by NASA is shown below, it consists of 1 degree resolution (the 1/4 degree data was not available at the time of writing).

The image is supplied as a 2400x2400 pixel bitmap where each pixel represents about 2km. The height at each pixel is represented as a 2 byte unsigned integer, 1 unit representing 1m.

OpenGL

The following renderings are snapshots from an OpenGL version of the middle third of the dataset centered on the pole region. With the hardware configuration, this 800x800 grid wa the limit for interactive flying in OpenGL (Dec Alpha XP1000 with 4D51T OpenGL card) Note: there is extreme height scaling factor of 2000 in these images!

Appeared on the cover of HPCWire magazine on August 17, 2001

POVRAY

In order to render the entire 2400x2400 grid POVRAY was used primarily due to it very efficient "height_field" primitive. In the following renderings the height scale factor is

Source code example for POVRAY

height_field {
   png "mars.png"
   smooth
   pigment {
      color rgb <0.8,0.8,0.8>
   }
   normal {
      bumps 0.5     // The height of the bumps
      scale 0.002   // The spatial scale
   }
   finish {
      ambient rgb <0.2,0.2,0.2>
      phong 1
   }
   translate <-0.5,0.0,-0.5>
   scale <2,0.2,2>
}

There are some artefacts in the data, the following image shows streaks which illustrate missing or corrupt laser paths.

Online Rendering of Mars

NEWS
This system has now been turned off. It ran for about a month and received a huge number of hits, unfortunately the cluster it used to do the rendering has other more pressing activities. Feel free to explore the image gallery of interesting renderings created while the system was operational.

This experimental interface lets you create your own personal renderings of the topology of Mars. Simply fill in the form below and submit it. You will receive an email indicating the eventual URL of the rendering. Typically your rendering will be ready within 30 minutes but it may take longer depending on the current load on the farm and the number of other renderings running at the same time.
The image gallery has some renderings already created by others.

Longitude: degrees
Latitude: degrees (-80 to 80)
Range: km (3800 to 15000)

Height scale: (1 to 20)
View direction:
Camera Aperture:
Light source:
Add CO₂ clouds:
Email address:
Help and additional information

The renderings are run on the high performance clusters at Swinburne University and managed by the Astrophysics and Supercomputing Group. The geometry is derived from the MOLA (Mars Orbital Laser Altimeter) 1/32 degree topology dataset.

For more information, suggestions for improvement, and any problems with this system please contact me (Paul Bourke) by email.