Getting RGB from barycentrix coordinates
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On 25/06/2014 at 09:54, xxxxxxxx wrote:
Suppose I add a gradient material to an object.
I'm trying to get the color values for that gradient from the barycentric locations of the polygons.
I have a ray collider that gets the barry coods. And the polygon face ID#s.
But I don't know how to get the color values.In your last video you pick a color by selecting some verts. And I'm wondering how you're doing that? And I'm also wondering how I can get the color value not just from a vertice. But also anywhere within the hit polygon at the barry coords.
-ScottA
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On 25/06/2014 at 12:50, xxxxxxxx wrote:
My methods will not help you, I'm afraid, Scott
You need to sample UV coordinates from the surface and sub-UVs (barrycentric coordinates).
My method doesn't deal with UVs. In fact, it is all about NOT using UVs and, instead, have RGB values assigned to each vertex.
These RGB values are stored inside a BaseContainer that is inside a tag that must be attached to polygonal objects. -
On 25/06/2014 at 13:47, xxxxxxxx wrote:
I was afraid of that. I don't think I'll ever find an answer to that.
Thanks anyway.I did try out what you're doing though with the RGB vertex colors.
I'm assuming that you're using the DisplayControl() method to set the colors?
I can set the colors of the vertices using that method. But I'm not getting good results from it.If I set the four vertices to the colors: red, green blue, black. I get a polygon consisting of a yellow triangle and an aqua color.
But you seem to be able to color the polygons with a falloff to them.
I'm curious how you're using the barycentric values to control the colors and the blending.
If you aren't going to sell this plugin. I'd like to see the code to learn from it.-ScottA
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On 25/06/2014 at 14:12, xxxxxxxx wrote:
I use two methods to display the polygons in color.
The fast method is through a scenehook, using the DisplayControl, that simply fills the cds.vertex_color[n] with the RGB values.
I also set the cds.vertex_color_shading to TRUE.
This method has the disadvantage of only showing the color when the objects are selected.The other method is slower but it displays the shaded polygons all the time. It uses DrawPoly and that method already works with shaded vertexes also.
I'm going to sell the plugin but we can talk through PM or mail, if you want to ask and check more stuff about my code. I bet it is not a very clean code (after all, I just started coding in C++ two or three weeks ago) but it is working
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On 25/06/2014 at 14:18, xxxxxxxx wrote:
However, if there is a way to bake textures (and it sure is), if you find a way to do it internally, you can easily find the values of the RGB inside the polygons. At least in theory, I guess
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On 25/06/2014 at 14:57, xxxxxxxx wrote:
I'm using the overloaded DisplayControl() and cds.vertex_color[n] in a tool plugin to play around with it. I don't think I want to get into the whole Scene hook thing for this.
I was just curious why setting a color value for four corners of a polygon makes the polygon split up into two colored triangles. With no blurring.
I was expecting to get a polygon with red, green, blue and black corners that gradually blended together. But instead I got this split polygon result.
I thought maybe your code would help me understand it better. But if you're going to sell it, don't worry about it.The other problem of getting the the RGB color values from the polygon's barycentric position is something that I've wanted to know how to do for years.
Some people say they know how to do it. But then they never show any code on how to do it.
It's become my white whale.
-ScottA
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On 25/06/2014 at 15:10, xxxxxxxx wrote:
I didn't know that we could use the DisplayControl method in a plugin that was not a sceenhook
Did you set the cds.vertex_color_shading to TRUE?
If what you want to know is the interpolated RGB value, from a barrycentric coordinate, if you know the RGB values of each vertex, I can tell you how I did. I used the barrycentric coordinates returned by the GeRayCollider.
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On 25/06/2014 at 15:21, xxxxxxxx wrote:
Yes. There's two DisplayControl() methods available. One for a SH, and one for ToolData plugins.
I can't set mine to cds.vertex_color_shading. Because that option is not in R13. It was added in R14.I think I can get the vertice color values from my current toolData plugin's DisplayControl() code.
So I'd really like to know how you're getting the interpolated RGB values for the barrycentric coordinates.
What I really want is the material color values. But maybe your code getting the vertex colors will help me get there.-ScottA
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On 25/06/2014 at 15:33, xxxxxxxx wrote:
My code snippet at the top shows how I do it. I will paste it here again but I will comment it:
// these are the values returned from the GeRayCollider
// I don't know if you can get them in some other way.// the index of the polygon
f_id1=res.face_id;// a way to know if it is a triangular face or, if it is a quadrangle, if we are on what triangle of that quadrangle.
f_id2=res.tri_face_id;// the barrycentric coordinates
rr=res.barrycoords.x;
ss=res.barrycoords.y;// pol_abcd is a Cpolygon
// s_poly is a Cpolygon* holding all the polygons of the object
pol_abcd=s_poly[f_id1];// getting the point indexes
// for a triangular face, c will be the same as d
a=pol_abcd.a;
b=pol_abcd.b;
c=pol_abcd.c;
d=pol_abcd.d;// getting the rgb values assigned to the vertexes
// in my case, they are inside a BaseContainer
rgb1=s_store->GetVector(a);
rgb2=s_store->GetVector(b);
rgb3=s_store->GetVector(c);
rgb4=s_store->GetVector(d);// if f_id2==(f_id1+1) then the barrycentric coordinates
// correspond to a triangle or to the first triangle of
// a quadrilateral polygonif (f_id2==(f_id1+1))
color=rgb1*(1.0-rr-ss)+rgb3*rr+rgb2*ss;
else // it corresponds to the secont triangle of a quadragular polygon
color=rgb1*(1.0-rr-ss)+rgb3*rr+rgb4*ss;
I hope this helps somehow, Scott.
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On 25/06/2014 at 17:04, xxxxxxxx wrote:
OK Thanks.
I figured out why I was getting a split colored polygon instead of a gradient type result.
I was using the wrong color value range.I was using: Red = Vector(255,0,0)
But I needed to use: Red = Vector(1,0,0)-ScottA
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On 25/06/2014 at 19:01, xxxxxxxx wrote:
Yes. RGB is stored in 0..255 range but C4D (and others) store the values in the 0.0-1.0 range. Good to be aware of that difference.