# konstantin magnus

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1. ## Vellum, PBDs or....

To animate the spider web threads, you would pin the end points and set vellum to the constraint type 'string'. For membranes to 'cloth'. spiderweb.hipnc
2. ## Vellum, PBDs or....

For static models I mostly just fake gravity based on curve lengths or surface distances: https://procegen.konstantinmagnus.de/spider-web https://procegen.konstantinmagnus.de/minimal-surface-membrane Eg. for resampled curve segments on a spider web, a is the user defined hanging amount, u the relative and r the absolute length. u * (1.0 - u) is a function to make the curves hang in their center. float a = chf('amount'); float u = vertexcurveparam(0, i@vtxnum); float r = primintrinsic(0, 'measuredperimeter', i@primnum); v@P.y -= u * (1.0 - u) * a * r; spiderweb.hipnc
3. ## How would you create this kind of snow accumulation?

Cool, I've just replaced the iterative approach by a tracer that does practically the same thing. int steps = chi('steps'); float w = chf('width'); float dist = 0.0; if(f@mask < 0.5){ vector pos = v@P; for(int i = 0; i < steps; i++){ vector grad = volumegradient(0, 'height', pos); pos -= normalize(grad) * w; float mask = volumesample(0, 'mask', pos); if(mask > 0.5){ dist = 1.0 - i / (steps - 1.0); break; } } } f@mask = max(f@mask, dist); snow_accum.hipnc
4. ## Visualizing mesh thickness

Hi Isaac, in this case couldn't you work with one ray, eg. using the ray SOP with inverted normals? thickness.hipnc
5. ## How would you create this kind of snow accumulation?

Hi Ploy, you could streak the object mask on towards the gradient. heightfield_snow.hipnc
6. ## Seamlessly stitch two HeightFields

I think you would still need to correct the point numbers to really make all the tiles match, but yeah, I'm glad it's useful.
7. ## Seamlessly stitch two HeightFields

Copy the height fields to the points of an octahedron to shape a cube, apply noise there and assign them to a cross. Alternatively try sampling the world position noise from a cube mesh right away: int index[] = array(0,2,1,3,5,4); vector bb = relbbox(0, v@P); vector uvw = set(bb.x, bb.z, 0.0); vector pos = primuv(1, 'P', index[i@primnum], uvw); float height = noise(pos * 50.0) * 200.0; f@density = height; heightfield_cube.hipnc
8. ## Seamlessly stitch two HeightFields

Hi Natiq, maybe there is a node for this, but you could overlap both height fields and sample them into a new one: float band = chf('band'); float h_0 = volumesample(1, 'height', v@P); float h_1 = volumesample(2, 'height', v@P); float mask = smooth(-band, band, v@P.x); f@height = lerp(h_0, h_1, mask); hf_blend.hip
9. ## create string portrait

Hi Ping-Yen, we had this a while back: https://www.sidefx.com/forum/topic/79315/#post-341726
10. ## Low-poly helicopter on a CRT

A low-poly helicopter from a sweep and some extrusions. Raycasted to shine on a CRT monitor.. helicopter.hipnc
11. ## Volume Caustics

Thank you Tesan! I've just translated the first example from C to VEX for a volume wrangle. // Use Monte Carlo integration and ray marching // of signed distance field (SDF) to render emissive circles. // Source: https://github.com/miloyip/light2d/blob/master/basic.c int samples = chi('samples'); function float sd_circle(vector2 uv, pos; float radius){ float dist = distance(uv, pos) - radius; return dist; } function float sd_scene(vector2 uv){ float d_0 = sd_circle(uv, {0.3, 0.18}, 0.12); float d_1 = sd_circle(uv, {0.25, 0.18}, 0.12); float d_2 = sd_circle(uv, {-0.3, -0.2}, 0.02); float dist = min( max(d_0, -d_1), d_2); return max(dist); } function float trace(vector2 uv, dist){ float t = 0.0; for(int i = 0; i < 100 && t < 2.0; i++){ float sd = sd_scene(uv + dist * t); if(sd < 1e-5) return 1.5; t += sd; } return 0.0; } function float sample(vector2 uv; int samples){ float sum = 0.0; for(int i = 0; i < samples; i++){ float a = 2.0 * PI * ((rand(uv) + i) / float(samples)); sum += trace(uv, set(cos(a), sin(a))); } return sum / float(samples); } vector2 uv = set(v@P.x, v@P.y); f@d = sample(uv, samples); light_2D.hip
12. ## Mycelium growth

Hi Robert, yes, you can integrate the minimal surface position with the ray node or minpos(). I've added the pig head to the food input to motivate growth there, as well. mycelium_3d.hipnc
13. ## Line tracer infection

Hi @sessionbeer, not quite the same, but this one comes close: https://procegen.konstantinmagnus.de/growing-a-mycelium
14. ## signed distance outline curves

Here's a way to draw a 2D SDF-curve. sdf_curve.hipnc
15. ## Resample in VEX? (imitate Resample SOP | resample vector array)

Hi @Krion, the spline()-function can do this: https://www.sidefx.com/docs/houdini/vex/functions/spline.html
16. ## I need to find a way to detangle some spheres...

Hi Masoud, there are probably some particle operators doing the same thing faster, but you could pull and push a voronoi-network according to the point scales until all spheres are deintersected. deintersect_spheres.hip
17. ## Geometry Object conforming to another Geometry surface

Hi @virgile, you could blend positions based on their distance towards the surface: In a point wrangle with first input mesh, second input sphere: float d_min = chf('min_distance'); float d_max = chf('max_distance'); int prim; vector uvw; float d = xyzdist(1, v@P, prim, uvw); vector pos = primuv(1, 'P', prim, uvw); float mask = smooth(d_min, d_max, d); v@P = lerp(pos, v@P, mask); conform_to_surface.hipnc
18. ## Preferred scripting language for Renderman

What would be the current preferred language to script patterns for Renderman inside Solaris? Eg. turning UV coordinates into dots and stripes as color vectors or float masks: vector uv = v@uv; float d = distance( frac(uv*8), {0.5, 0.5, 0.0} ); float c = 1.0 - smooth(0.2, 0.5, d); v@Cd = c;
19. ## How to set normals to look up

You would need another vector called "up" that points upwards, eg. v@up = {0,1,0};
20. ## Keep primitive attributes when I save as obj

Hi Mani, before exporting you can promote primitive attributes to vertex UVs and/or vertex normals and promote them back after importing the OBJ. Wikipedia describes the OBJ-format: The OBJ file format is a simple data-format that represents 3D geometry alone — namely, the position of each vertex, the UV position of each texture coordinate vertex, vertex normals, and the faces that make each polygon defined as a list of vertices, and texture vertices. obj_attrib.hip
21. ## Questions about edgeequalize node and topology. thanks

Try the circle from edges-node in case the holes are supposed to be circular.
22. ## coplaner polys inside another wanting to remove

Hi Curt, did you look into the hole SOP?
23. ## I need some advice on the ripples of the ship.

There is a Kelvin Wakes deformer in SideFX Lab's now: https://www.sidefx.com/docs/houdini/nodes/sop/labs--kelvin_wakes_deformer-1.0.html
24. ## Blend positions between uneven topology meshes

How would you blend positions between meshes with different topology and uneven point count? My idea was to use the 'underlying' primitive's intrinsic UV coordinates for matching. But when transfering to world position I run into this typical "fix boundary seams"-issue known from the UV texture-node. blend_pos.hip
25. ## How to vertically align a uv texture?

Polyextrude does UVs. Just assign UVs on the grid in advance and ignore the viewport issue that comes later. extrude_uv.hip
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