Blendergis DEM object not colliding

Dear all,

Being completely new to everything blender and 3d modelling i have run into an issue.
What i would like to achieve is making a 3d terrain model and being able to do some terrain analysis and visualisation using fluid simulation.

Using BlenderGIS i have made a 3d recreation of the terrain I would like to use, but when i try to incorporate this in a fluid simulation (using quick liquid) i just cant seem to get the fluid to collide with the 3d model that comes out of BlenderGIS.

I have tried to make the surface thickness way thicker, i have solidified the faces using edit mode, i have tried to use it as a guide instead of collision in the effector selection, and i have used the fractional obstacles with obstacle-fluid theshold to the max.

For some reason the fluid keeps passing through the terrain model.

I hope someone here could point me in the right direction.
I dont know if this is a common problem with objects created through blendergis? the way i use blendergis now is DEM raw data, and letting blendergis create the faces.

As a new user i cannot yet upload a file, but when i can i will add a blend file


It’s so difficult to help without a file or even some screen shots of your setup.

Will the fluid collide with other objects in the scene?

Check the normal direction of your landscape object perhaps? Use the Viewport Overlays and tick the Face Orientation checkbox. The faces of your object should be Blue if the normals are pointing outwards correctly.

It could be that Mantaflow is just replaying back the cache from a sim where the collision was incorrectly set up. Rebake the sim to be sure to flush the old cache. This has caught me in the past. On Replay Mode Mantaflow only appears to flush the cash when you change setting in the Domain not when you add effectors to other objects or move them around etc.

Just change the resolution division up then down and the cache will be overwritten on next playback.

See how that goes for you.

As soon as my forum user status allows me i will upload the file, in the meantime i will try your tips, much apreciated!

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Do drop back and say if any of the tips worked, then someone else may benefit from this thread.

I checked the face orientation and it showed up blue (being correct, im assuming)

when i add standard object into the simulation and mark them as an effector fluid collides with them after i rebake, just the terrain model does not.

I have uploaded my blendfile to my google drive, if anyone could have a look at it, it would be greatly apreciated!

link to file:

The problem is with the geometry it looks malformed. It almost looks like there are several layers of geometry on top of each other.

I would try creating it again and perhaps use the Solidify modifier to add thickness then apply the modifier.

Wow, Infograph, it seems like adding the solidify modifier seemd to do the trick, i cant really get my head around why this helped, but it seems that it did!

i seemd to have cheered to soon, but i will keep experimenting with the modifiers

Did you recreate the geometry in BlenderGIS then apply the solidify modifier?

Maybe go back to square one, forget the landscape and just use simple primitive objects to get your head around Mantaflow. Once you understand how the fluid sim works then think about bringing in a BlenderGIS object again.

It’s critical that the landscape object has a significant thickness otherwise the liquid particles will pass through even with plenty of sampling substeps.

Here’s my test using the Landscape Addon which ships with Blender. I just added a solidify modifier, applied it than added the fluid modifier effector/collision settings.

that is exactly what i am trying to achieve! for some reason all other objects im adding into the simulation collide like they should, but not the blendergis object, i will look into the landscape addon you mentioned and keep experimenting with the blendergis object

Maybe I’ll take a look at BlenderGIS myself, I have been meaning to for a while, and see if I can find what the issue might be.

The landscape addon is pretty cool.

Its a very nice addon! Professionally I’m in military intelligence and I’m trying to use BlenderGIS to visualize certain terrain aspects. There is a lot of potential in using 3D models of the actual terrain for analyzing that is not yet being used.

update: it is now working somewhat, what i have done is exporting the BlenderGIS object to a wavefront obj. then after importing this the object is colliding with the fluid! still having some finetuning to do, but this is a very big step forward.