Artists Guide

There are two main areas where we artists can contribute. We need 3D models and textures for the same and the landscape.

Textures

We use the CC-by licence for OpenClonk and ask you to license your contributions under the same license. As many textures in texture archives have licenses which are not compatible with CC-by, we will have to create many textures on our own. But don't worry, it's quite easy and there are some really good tutorials on how to create quality textures from photos.

There is a list of bigger texture archives and it's licenses which is a good source for ressources: Texture Archives

How to create seamless textures

Especially for material textures, we need seamless textures. There are different methods to create seamless textures from (a set of) photos, here is how I do it: Tutorial: Creating Seamless Textures.

For GIMP, there are two filters which can do this automatically: The plugin Texturize and the filter Resynthesise. Both work good with textures with small random patterns like gravel, plaster, sand or ground. However, they don't produce quite as convincing results for bigger regular patterns like (roofing) tiles, bricks, wickerwork, pavements etc. The manual method that I proposed always produces better results and if you are experienced in this, it's a thing of five minutes.

How to create normal maps for textures

If materials or models get normal maps or not is still in question. However, here are two good tutorials how to create normal maps from photos.

• From photograph to normal map, how to... - Excellent tutorial including tips how to photograph right
• Creating Normalmaps - Very practical but little background information

Modelling

The size in which the graphics are displayed will be about 3x as big as that of Clonk Rage. Additionally, it is planned to directly render the bigger models in game (real time rendering), most probably with OGRE.

Models for real time rendering

Now, if you are used to create models to render them afterwards, you need to take into account a few additional things:

• The models need to have a low polygon count. Details like e.g. rivets which you perhaps used to model before are drawn in the texture. The texture is a very important part of the model. Thus, creating a very good and clear UV map for your model is a necessity (Tutorial for blender). It not only affects the quality of the texture map, but also of any other maps like normal maps or reflection maps.
• The guideline on how low-poly the model should be is: The model with texture still needs to look good when displayed 3x the size as in Clonk Rage - there is no fixed number on how many polygons are good since it depends strongly on the model.
• You should delete the faces that are not visible from where the model is looked at in the game. These include faces that are just not visible from any direction because they are inside other objects but also faces which will never be visible in the game. For example the backside of a house or the bottom of most models will never be visible. However, this process is very fast when you do it when you are done with the model - just before you create the UV map. So don't worry about it while modelling and also don't overdo it - A few polygons on the back of the house do not matter so much.
• Always start with the low-poly model, it's much easier to start of with a low-poly model then to first create a high-poly model and then get it down to a low-poly count. You can always add details later, either in the texture or in a high-poly model. In Blender, there is a option called "multires" which allows you to create several models in different detail levels based on one low-poly model and it's geometry. Baking normal maps (Tutorial for blender) with a high- and a low-poly model only works if both have the same geometry.
• Creating normal maps for models only makes sense for those which have organic, round parts where too much polygons would need to be used. So, for buildings it's normally not necessary - more for living creatures with one (Blender: example) enclosing mesh.