I learn best by application. Following tutorials without a goal in mind doesn't help me as much as actually doing something with a purpose. I have been developing my inkscape techniques with each new image I create (or copy depending on how you view it). I have created some really cute cartoony animals using mostly circles (converted to path and then changed shape) and a few lines. For me, it was a great way to get acquainted with those three simple tools. (see attached example. I made a panda with a head band holding a warning sign.)

I have also traced or reproduced various graphics that I admired or otherwise wanted to use in some way. I did a funny greeting card up in SVG from a PNG I found on the net that turned out well. I did "Homer Hulk" (fairly famous picture... just google it and switch to images) up in SVG... it's pretty accurate and now scalable! Then one day I came across an awesome desktop wallpaper thread on one of those image forums and in there was a "Dark Side of the Moon" Pink Floyd album cover mock up except the triangular prism was the Darth Vader helmet and mask. I could never find this image except in a bitmap format but was able to find it in 1600x1200 and that was helpful but this image was originally done in a vector format and have been disappointed that I was unable to find it in that format anywhere. I did find this though:

http://www.whiz.se/backgrounds/dsotm/

That's done up in SVG and was a good starting place so all I needed to do was reproduce the "crystal" vader helmet and mask. Took some time to figure out a way I was happy with, but I have done that as well.

So you can see I have all the elements to compose the picture I wanted... and I did. But now it's not good enough and I don't know how to get there in a way that I am satisfied with.

The rainbow rays are flat colored shapes arranged in sequence. I want them blended nicely. My first attempt was to take the existing colored shapes and do a gradient transitioning from its original color to the next color. It was "okay" but never looked right and now I have figured out why. Next, I tried to create a single object with of the rainbow spectrum ray and just fill it with a rainbow gradient. I was quite successful in creating a rainbow gradient I was happy with where it started from transparent to red, then through the colors and ending with purple to transparent -- exactly what I wanted. The trouble is, gradients can only do parallel as far as I can tell. I can make it circular or I can make it linear. But I can't make it expand on one end the way the rays in the "dsotm" image does in a gradient form.

I found the "make a rainbow" tutorial and found it interesting, but I don't know those particular tools well enough to know what I am doing but it also seems very "row & column" and might not be suitable for what I want (which I hope by now is more clear). But I imagine I might end up with an array of strokes where the stroke paint expands wider as it progresses, but I am not sure how to do that.

Anyone have suggestions, ideas or even a "how to"?

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Quick follow-up:

I did experiment with using a method similar to the rainbow creation method using the clone tool where I created one object and tweaked its clones. At first I created a single thin gradient box and cloned it while expanding its width. This came pretty close but looked choppy even with blur on it. (I might have been able to do something more useful with it if I could convert the clone objects to path objects... from there I can do more things with them.) Another try involved using the clone tool to copy a single red line and, using a technique similar to the rainbow tutorial, creating the clone array while shifting the hue to create the rainbow. If I tweaked with it enough I might have achieved exactly what I was after but there was another problem. It seems that by having 30 - 50 clone things and then processing blur on them, it takes a lot of processing power to render. So that was no good even if I could get that to work.

I am beginning to think i will have to cheat by creating a large bitmap and embedding it into the image. It feels like a dirty cheat though and I will never be satisfied with it knowing I cheated.

Perhaps there should be some sort of way to create a sweeping gradient, but I think that might depend on whether SVG can support it within its format. Still hoping for someone with expert knowledge to chime in...

what is your specific question please?

vwanweb wrote:what is your specific question please?

Specific question is:

How can I make a gradient filled object fan out? As a light spectrum from a prism spreads the light out, I would like to create this without using multiple objects.

trying to think this through, do you have web page you could post here as a reference of what you are trying to create please?

-vw

vwanweb wrote:trying to think this through, do you have web page you could post here as a reference of what you are trying to create please?

-vw

I suppose showing you here would be just as well. See the attached example.

Thanks for the reference file, I have three possible suggestions, outlined in the attachment..

1. Once you are finished with the spectrum of colors, to get rid of the nasty lines between the 6 colors of your work. Duplicate (Ctrl+D) the 6 objects this will minimize the nasty lines. I use this whenever I work with patterns too.

2. Make a bitmap copy (Alt+I)of your spectrum, blur the bitmap, then draw an outline path ABOVE and around the edge of your spectrum colors, select both the Blurred Bitmap and the New Path, right Click and Set Clip (>Object >Clip>Set)

3. Scratch all of the above and create 6 paths of the colors you want to use, set stroke width at 1.0. Convert the Stroke Segments to paths, >Path > Stroke to Path.
select two adjacent paths (i.e, Red&Yellow) then use >Extensions >Generate from Path >Interpolate...
Method 1
Steps ~16
Interpolate Style X (Checked)
Note: the interpolate style works best with two colors that are separated by one color (using the Color Wheel (Ctl+Shift_F) as a reference). As an exampe Red and Yellow are separated by Orange. If the colors are not close neighbors in the color wheel then this filter will use Saturation (Gray) to step between two colors.

-vw

vwanweb wrote:Thanks for the reference file, I have three possible suggestions, outlined in the attachment..

1. Once you are finished with the spectrum of colors, to get rid of the nasty lines between the 6 colors of your work. Duplicate (Ctrl+D) the 6 objects this will minimize the nasty lines. I use this whenever I work with patterns too.

2. Make a bitmap copy (Alt+I)of your spectrum, blur the bitmap, then draw an outline path ABOVE and around the edge of your spectrum colors, select both the Blurred Bitmap and the New Path, right Click and Set Clip (>Object >Clip>Set)

3. Scratch all of the above and create 6 paths of the colors you want to use, set stroke width at 1.0. Convert the Stroke Segments to paths, >Path > Stroke to Path.
select two adjacent paths (i.e, Red&Yellow) then use >Extensions >Generate from Path >Interpolate...
Method 1
Steps ~16
Interpolate Style X (Checked)
Note: the interpolate style works best with two colors that are separated by one color (using the Color Wheel (Ctl+Shift_F) as a reference). As an exampe Red and Yellow are separated by Orange. If the colors are not close neighbors in the color wheel then this filter will use Saturation (Gray) to step between two colors.

-vw

Thanks for all of that. Most enlightening. I was already on that path. The problem is that when it starts rendering, it really taxes the computer which is why I would like to see some sort of gradient shaping or some such thing. Seems there is no better way than to make shapes as close as possible and slight blur. It's the lowest rendering hit possible. Perhaps as Inkscape and the SVG format develop more...

erroneus wrote:Perhaps as Inkscape and the SVG format develop more...

Diffusion Curves - if accepted for SVG and if implemented in Inkscape - will help to render such free form / irregular gradients.

~suv wrote:

erroneus wrote:Perhaps as Inkscape and the SVG format develop more...

Diffusion Curves - if accepted for SVG and if implemented in Inkscape - will help to render such free form / irregular gradients.

Well that is certainly worth hoping to be implemented. I think SVG's strength and power comes largely from the simplicity of description information and the resulting output quality. Being able to express a lot with simple elements does more than any compressed bitmap could ever do. I wonder how far off the technology for creating vector based video is? I think the results can be quite impressive eventually.

I haven't tried this, so don't know for sure if it will work, but I'm wondering if you could use radially tiled clones? And then of course you would not use the entire thing, just a partial "arc" (or slice of pie). I'm not sure how to get the specific colors to be applied to each clone, but someone else might know the right settings for the Color tab.

For me, I think I'd take a simpler approach, and make (roy g biv) 7....I believe they are called trapazoids, but grade school math is many, many years ago . Basically an isosceles triangle with the most accute angle's point cut off. 7 of them, each with appropriate color, put side by side, and blur them. Also don't know if this will work because I haven't tried it, but it's my 1st, best idea

brynn wrote:I haven't tried this, so don't know for sure if it will work, but I'm wondering if you could use radially tiled clones? And then of course you would not use the entire thing, just a partial "arc" (or slice of pie). I'm not sure how to get the specific colors to be applied to each clone, but someone else might know the right settings for the Color tab.

For me, I think I'd take a simpler approach, and make (roy g biv) 7....I believe they are called trapazoids, but grade school math is many, many years ago . Basically an isosceles triangle with the most accute angle's point cut off. 7 of them, each with appropriate color, put side by side, and blur them. Also don't know if this will work because I haven't tried it, but it's my 1st, best idea

The way to assign colors to clones is to tell it to shift the hue value by an appropriate percentage. But when you do all of that, you either end up with too many objects or a non-smoothe transition between colors or both. And trying to blend with blur just slows things down pretty badly. The present best is to create between 6 and 8 objects each containing a two-color gradient. And this only works when the fanning-out of prism/rainbow angle isn't too great. The problem with gradients is that they are parallel or radial only which would seem to limit things considerably. On the other hand, if the objects were elongated triangles and the center point of the gradient was in the center of the triangle and the gradient was a three color gradient, the parallel-ness might not be as harmful to the look. In any case, it's not optimal.

In this case, the best possible way would be for a gradient to have two or more segments to define how it flows so that on one end, the gradient would be tight and narrow and the opposite end, it would be wider.

As someone responded earlier, having gradient follow a curve would be a move in a good direction though I am not entirely convinced it would help in this particular instance. Vector graphics are not without its limitations.

In any case, the finished image essentially used the technique you described though I didn't use clones.

well if the taxing of your PC's resources is a major issue one way to do this is to make a single object rectangle then apply a multi-stop gradient to it. This leaves you with one object, with a rainbow gradient fill. If you are concerned with the quality loss when using bitmaps you could select the rectangle and use Ctrl+> to scale it +200%. Export this enlarged graphic then use Imagelys picture styles (freeware) to transform the perspective of your rectangle. The perspective features in inkscape will not give you what you are looking for, Imagelys will. Import your work from Imagelys Select it and use Ctrl+< to reduce it at scale -50%.

Well, the crux of the matter as I understand it is that Inkscape does not support sweep (conical) gradients. I am not sure if this is a shortcoming of SVG or if it is also a planned future enhancement to the gradient tool.

While I certainly don't want Inkscape to just copy features of other programs conical gradients have been an important feature of digital graphics for quite a long time - (I wonder how many people here remember Kai's Power Tools for Photoshop...?)

druban wrote:Well, the crux of the matter as I understand it is that Inkscape does not support sweep (conical) gradients. I am not sure if this is a shortcoming of SVG or if it is also a planned future enhancement to the gradient tool.

SVG 1.1, the current SVG specifiaction, does not support conical gradients, only linear and radial.

Inkscape developers will be very careful and AFAIU rather not implement a new feature based on draft versions of the next SVG specification (see what happened with the 'Flowed Text' implementation and how frustrating it can be for all coping with an object type in use that will not be part of the next SVG specification and is not recognized by most SVG viewers). Gradient meshes, conical, free-form gradients and (lately) diffusion curves are often requested feature enhancements, but - again AFAIU - adding any to Inkscape will depend on what will be part of the next SVG spec.

See also:
Advanced Gradients - Inkscape Wiki
Diffusion Curves - Inkscape Wiki
LGM 2010: Jasper van de Gronde: Diffusion Curves in Inkscape vector drawings | River Valley TV
SVG WorkingGroup - Inkscape Wiki