Use knife at a precise height

Hello,
I have modelized a sofa with precise dimension in cm.
Sometimes I needed to use the knife to do a straight cut starting at the precise point.
So I tried to snap the knife tool to my 3D cursor that I precisely positioned but it doesnt snap to it.
Is there a way to do that ?
Thanks !

Blender’s knife tool is rather crude. When you need precision, you can model your cut using simple geometry (e.g. a plane) which you can position precisely like any other geometry. Then select it and do a Face -> Intersect (Knife). Then simply delete what’s left of the cutter.

Ok thank you !

Thanks ! The tool “Tiny CAD” does what I wanted .
The function is called “XALL intersect selected edge”, very useful.
You can find my project here : https://pasteall.org/blend/ee060c9dffe3444db948bb40cf95f422
Would you know why my velvet texture does apply of my sofa but not to my sofa ?
That would help :slight_smile:Thanks !

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You’re using UV coordinates for texture mapping. The cushion was made from a cube and already has the UVs that came with the cube. The sofa, however, doesn’t even have a UV map, which means all texture coordinates for it map to (0,0). TLDR: you’ll need to UV unwrap the sofa. Although I’d suggest to first fix the geometry on it, there are some problems like internal faces and disconnected geometry.

Thank you so much! I thought UV unwrap was for image texture only.
How do you see internal faces and disconnected geometry ? is there a tool to see it ?
Thanks again !

Select -> Select All By Trait -> Non-Manifold. Use it in vertex or edge mode. This will highlight problematic areas on your mesh.
The internal faces, however, might not be highlighted, because on your actual editable mesh they’re not internal yet. You’re using the mirror modifier which mirrors everything around a plane. But you have faces running along this symmetry plane. The modifier mirrors those as well, merges them, and so your final result ends up having faces inside. When modeling with a mirror, make sure to delete any faces that lie on the symmetry plane.

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thanks a lot !