Photo-realistic - Terragen compared to L3DT

[3DUser]

Terragen advertises that it can make photo-realistic landscapes. The Terragen 2 gallery results on its website indicate this is accurate from a quick,visual inspection.

Since I'm new to L3DT and could not find a mention of that capability here, will L3DT produce photo-realistic landscapes? Just thought I would ask.

[tillot]

No. It does produce textures, but they are not produced via photorealistic techniques like ray-tracing & radiosity.

Many people use the L3DT to generate a heightfield and then render it in another software package like terragen.

Example:
L3DT -> Produce very large heighfields. (usually a large number of tiled height fields.)
EarthSculptor/Daylon Leveller/FreeWorld 3D/Pnp Terrain Creator -> Edit the heightfield tiles you need to place buildings on, create roads, etc.
Terragen/Vue/Bryce -> render photorealistic texture for each heightfield tile
Lightwave/Maya/Max/Torque Game Engine Advanced -> Import heightfield and texture map to scene. Make animation or game.

[Aaron]

Hi 3DUser,

I'd like to clarify this if I may:

Terragen is a photorealistic renderer, and L3DT is not a renderer of any kind, so you must use another renderer to view L3DT landscapes. The quality of the landscape images you get is dependent on the renderer you use.

Now, to be a bit more specific, Terragen is photorealistic because it adaptively generates detail (bump-maps, lighting, etc) dependent on the camera view. For photorealism, this will take hours or days per image, and if you decide you want a different viewpoint, you have to start all over again. If you want to fly around the map, too bad, it won’t do it*.

L3DT generates terrain and textures principally for real-time renderers. These programs have to render the landscape tens or hundreds of times per second, so they don't have the time to do all the tricks done in Terragen. L3DT can do some of the heavy-lifting for the renderers by pre-calculating large, detailed light maps and textures. However, Terragen has the advantage in that it can generate high detail close to the camera and lower detail away from the camera. L3DT in contrast has no idea where the user will put their camera (think of a game; the camera can go anywhere), so if you want highly detailed textures, you have to generate the whole lightmap and texture at high resolution. This takes a lot of space and time, and to hit photorealism you would have to use an absurd amount of disk-space (tens/hundreds of gigabytes?), not to mention do some very fancy climate work, and make a 3D renderer that can cope with the data involved.

On the flip-side, Terragen is not particularly good at generating textures/light maps for realtime rendering. You can get this data by generating birds-eye-view images of the map, but if you’d like to do a high-detail texture (say 16k x 16k, which is fairly typical these days), it will either take forever or you will run out of RAM. Furthermore, Terragen does not generate alpha maps, which are also used for high-res texturing in realtime renderers.

So, in conclusion, Terragen and L3DT are not competitors; they exist for different purposes. Which is better depends on what you want to do.

Cheers,
Aaron.

* TG2 does have a fly mode, but it’s not photorealistic.

[3DUser]

Thanks to both of you for the detailed answers. This opens more possibilities for use of both packages. Also, thank you for the easily understood answers as well.

Regards.