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View Full Version : Vector vs. Raster - when to use which?



Chgowiz
01-30-2009, 10:02 AM
This is a subject that I asked privately, but I thought it might be useful to other hobbyists. We have an embarassing rich set of tools to choose from, Inkscape, GIMP on the freeside, Campaign Cartographer, Dunjinni, etc. So much so, that it is confusing to know which to use when.

I've been learning GIMP for awhile now, but I see people talk about vector based tools. I was curious to learn the differences and uses between the two, and I have found there's not really a clear cut definition of when to use either raster or vector. From what I understand, it seems that if you want smooth lines, non-pixellated text, or the ability to scale, you use vector. If you want textures, fills and other effects, you use raster. I'm not sure that's the whole story.

So I'd like to ask you all - when do you use vector vs. raster and more importantly - why? In talking to rank beginners - what should they learn from each tool and when does it make sense to use each tool?

Thank you.

Steel General
01-30-2009, 10:29 AM
I almost always use raster, mostly due to laziness more than anything else - but I'm sure others will be along and give you a more complete (and much better) answer.

RobA
01-30-2009, 11:13 AM
I tend to bounce back and forth between the different tool types.

I use vector tools for shapes I want good control of, i.e. text labels, roads, rivers, icons, symbols.

I tend to bring these as vectors into my raster software then convert them at the scale I need and then rasterize them and add effects, like texturing, shadows, etc.

-Rob A>

Redrobes
01-30-2009, 11:30 AM
Its all about the flexibility really. Ultimately everything (save the most extreme examples) gets rasterized but by using vector lines the rasterization process can be optimal at whatever scale it needs to be done at so you can use multiple scales and have one vector map.

Its neigh on impossible to vectorize a photo however. The best you can do is quantize the colors into bands and vectorize those bands. It can look alright but you can usually tell. If those colors are solid like a logo or a font then it can be better to vectorize them however.

If all of your raster icons, textures and other source bitmaps are a lot higher res than the highest final version of map you want to make then there is minimal loss of accuracy by using these high res sources to make a lower res map. Thats why having all the source textures nice and high res is important.

So on to convenience. Its much easier to modify a vector line than it is to modify a rasterized one. Theres other math things that are much easier on vector lines too - like ensuring that the ends of two lines are linked perfectly or ensuring that circles are really circular etc.

Finally, its pretty easy to raster a vector line optimally but its harder to vectorize a raster line. Well ok a line on its own isnt so hard but generally its harder to vectorize raster stuff than rasterize vector stuff so it can be a kind of one way process in many cases. So people might make initial stuff in vector, modify it and then raster it and do all the fills and bitmap stuff from there on. Knowing whats good about each is the key tho. I always advise that you should be familiar with one of each type of app.

ravells
01-30-2009, 11:39 AM
I tend to start in vector for general shapes and fills etc and then port it over to a raster editor to add textures etc.

Korash
01-30-2009, 12:19 PM
begining to learn both Gimp and Inkscape (and going slow due to time constraints :() and I have a question for you.

I have seen reference to "rasterising" a vector image a couple of times, and I can't figure out if that just means bringing it into a raster prog (ala Gimp) or there is something I need to do in Gimp in order to rasterise it.

some guidance would be helpfull here. :)

Thanks muchly

Midgardsormr
01-30-2009, 12:35 PM
Well, I don't know about the Gimp, but in Photoshop, you can rasterize a vector layer by right-clicking on it and choosing "rasterize" or by going through the layers menu. Generally speaking, I don't rasterize something until I need to add effects to it. As was mentioned, it's a one-way street. Again, though, I don't know how Gimp handles imported vector work.

Now, choosing between starting in raster or vector, for me, depends on the kind of image I want to produce. For textured maps like Mennin's Hallow, raster is the way to go. I can't imagine trying to do something like that in Illustrator. For clean-looking images like that Wheel of Time map I did recently, vector is the tool of choice. Best of all, though, is a combination of both. HandsomeRob's atlas maps are done with a combination of the two--raster for the shaded relief, and vector for the linework.

Redrobes
01-30-2009, 12:39 PM
A vector line is a math representation of a line with either two end points or one starting point and a direction - all just numbers.

Raster is a bunch of dots in a grid which have colors assigned to them to make up the image.

Rasterizing is where you go from something into a raster set of pixels. So what happens is that the app runs down the math line and colors in the dots. Its a little more complex than taking the closest and making it black on a white background for example as most measure the distances from the exact math line to the square pixel position and shade it darker the closer you are so it looks smoother and better.

So apps like say inkscape can export the math vector data to a raster version where it will do all that processing for you and leave you with a rastered bitmap - a rectangular set of pixels stored in a container like a JPG or a PNG.

Going the other way involves looking at the rectangular set of pixels and trying to best fit a line onto the darker pixels. Thats a more inexact science and different programs will give different results - some better than others.

Gamerprinter
01-30-2009, 12:49 PM
Then of course, the exception to the rule, there's me and Xara.

Since Xara, though primarily a vector application has some hybrid raster operations built within it. I (as I always say) use Xara almost exclusively.

The question would be when do I use raster? Sometimes a texture is not condusive to my goals, so I image edit in PS or GIMP. I clean up images, alter colors, use cloner brushes to fix details. If I use 3D objects, which are rasterized before using them further, I do the fixes in PS/GIMP.

I almost never bring a map back into PS/GIMP to finish it. All compositing, texture filling, not to mention grids and labels are all done in vector.

I don't think I would ever totally create a map in GIMP - not my aesthetic or preferred method of operation.

I would like to learn to create bump maps better in GIMP, then I'd finish my maps by doing that - but that's the only thing I can think of to use GIMP as my final step in creating a map.

GP

Redrobes
01-30-2009, 01:16 PM
Hmm ok better talk about texture mapping then. This is where you take a raster image and apply it into a vector space which is usually a 3D polygon for 3D models but it can also be a vector 2D area too.

What its essentially doing is resampling the raster texture but its not doing it with fixed scaling, the scaling is selected per pixel based on the vector shape so you can texture map a rectangular photo onto a circular disk for example. You can control the circle shape in a vector way and the image inside is a raster photo conforming to the shape of the circle.

I believe this is what Xara does and is what my ViewingDale does which allow both apps to scale up stuff using photo textures in a kind of vector way. In my opinion tho texture mapping is more of a raster process than a vector one. If you conform a low res photo into a shape and make that shape big then you will get the pixels showing up. If the photo was truly vectorized, which Xara can do very well too, then it would scale up perfectly but as said earlier it has to limit the colors and vectorize the bands within that photo instead of the full range of colors. So theres several options available but its just worth familiarizing yourself with all the options.

Wordman
02-01-2009, 03:55 PM
If you want textures, fills and other effects, you use raster.
Actually, most vector apps are just as capable of the first two of these as most raster applications; it's really the last one that is the big difference, as well as the "pixel tweaking" advantage of raster apps.

For textures, all you need to do is create a brush in a vector program and use it for fills. For example, take any 512x512 (rasterized) texture and make it a brush, and it will work just like a raster program (including the crappy scaling). You can also, however, create vector patterns that can be used as textures, which are a bit more flexible, but not by much. (They'll scale better, at least.)

For fills (gradients, etc), most raster and vector apps seem to be about the same. Vector apps might have a slight advantage of being able to follow paths with a fill, but this is pretty advanced, and not many apps can do this.

Most of the effects available in a raster app (which work by doing math on the pixels) simply aren't possible on most vector systems. Naturally, there are some effects that only work on vectors but, for most map work, these don't really matter. Some vector apps use a strange hybrid, where they "remember" a series of raster effects to apply to an object and, after the vectors are rendered to to a screen buffer, apply the raster effects. This isn't really the same, though, as altering the pixels directly.

Chgowiz
02-01-2009, 04:54 PM
Thank you to all who've responded. What I have learned from this is that while I can do a great deal with one or the other, there are some options that I may consider in using both. It sounds like I just have to try them out and see what works.

Thanks!

Nomadic
02-01-2009, 05:32 PM
For me personally I have found that if I want to do a realistic map that raster is much better. For simple/fast maps though vector is the preferred choice (as you can spit out a basic map much easier with it).

Gamerprinter
02-02-2009, 12:49 AM
For me personally I have found that if I want to do a realistic map that raster is much better. For simple/fast maps though vector is the preferred choice (as you can spit out a basic map much easier with it).

Hey Nomadic, I have to disagree... the following map is already posted in my Paizo Map Attempt thread in the Building WIP forum, however, I am posting it again for emphasis.

The following map was completely created in Xara Xtreme, with never touching a raster application. Xara Xtreme Pro 3.2 is a vector application - with some powerful features.

Everything is vector shapes with raster image fills, feathering, different transparency filters applied, bevels and shadows. Only 1 hour of work in this!

Again, the Bogwood Swamp - Kingdom of Flies! (a vector created map!)

Thoughts!

GP

Nomadic
02-02-2009, 04:26 AM
Hey Nomadic, I have to disagree... the following map is already posted in my Paizo Map Attempt thread in the Building WIP forum, however, I am posting it again for emphasis.

The following map was completely created in Xara Xtreme, with never touching a raster application. Xara Xtreme Pro 3.2 is a vector application - with some powerful features.

Everything is vector shapes with raster image fills, feathering, different transparency filters applied, bevels and shadows. Only 1 hour of work in this!

Again, the Bogwood Swamp - Kingdom of Flies! (a vector created map!)

Thoughts!

GP

I have to disagree with this in turn. Firstly though I have to point out that what I was talking about was in regards to me. My mapping style is one that makes higher quality stuff with raster but works faster in vector. Secondly, as nice as xara is I actually prefer the look of maps done in photoshop/gimp as they tend to flow more naturally. This of course isn't a hit against you as you do great work. I have noticed though that most vector maps can't get stuff to flow right. An example here would be within your map the artificially sharp mountain peaks and the way that textures suddenly turn into other textures. Vector isn't good at realism, but it is good at simplicity and cleanliness (it is for this reason that I do my cartoonography in vector programs).

Redrobes
02-02-2009, 02:10 PM
There are raster operations and vector operations and Xara can do both. If it loads in bitmaps and textures with them then its doing raster operations. Xara is a hybrid app. Although PSP, PS, Gimp are all hybrids too, I think Xara has what appears to be the best hybrid operations in its class. But you cant say that Xara is a purely vector app because your map is painting pixels by looking up into a bitmapped texture source - even if the shape your texturing is a vector shape that still essentially a raster operation. You can definitively say its a raster operation when you scale an image huge and it pixellates. Neither vector or raster is better in absolute terms they are just different. Some operations are easier to do vector and some raster. Having an app which does both does mean that you don't need to learn two apps but the point is that you need to know which operations are easy in either case. You can draw a line in raster apps and you can fill with pure vector patterns too and sometimes thats the right thing to do and other times its not so good but most would agree that its easier to draw and modify a line in a vector app and a patterns in a raster app. I don't think that its necessarily true that quick or realistic is the right split to say vector or raster as you can do either in either type of operation but some things are quicker in vector and some things and quicker in raster and likewise for realism too. Some things are easy to do in 3D and some things are really hard unless you do them in 3D - its just right tool for the job.

Nomadic
02-02-2009, 03:54 PM
There are raster operations and vector operations and Xara can do both. If it loads in bitmaps and textures with them then its doing raster operations. Xara is a hybrid app. Although PSP, PS, Gimp are all hybrids too, I think Xara has what appears to be the best hybrid operations in its class. But you cant say that Xara is a purely vector app because your map is painting pixels by looking up into a bitmapped texture source - even if the shape your texturing is a vector shape that still essentially a raster operation. You can definitively say its a raster operation when you scale an image huge and it pixellates. Neither vector or raster is better in absolute terms they are just different. Some operations are easier to do vector and some raster. Having an app which does both does mean that you don't need to learn two apps but the point is that you need to know which operations are easy in either case. You can draw a line in raster apps and you can fill with pure vector patterns too and sometimes thats the right thing to do and other times its not so good but most would agree that its easier to draw and modify a line in a vector app and a patterns in a raster app. I don't think that its necessarily true that quick or realistic is the right split to say vector or raster as you can do either in either type of operation but some things are quicker in vector and some things and quicker in raster and likewise for realism too. Some things are easy to do in 3D and some things are really hard unless you do them in 3D - its just right tool for the job.

True, but just to pipe in here again for a second. Again, I am talking about what works for me. For me my realistic maps are better in raster, but I can do maps faster in vector. That's not an opinion, it is a fact based on knowing how I work (and I am obviously going to know how I work better than anyone else just the same as they know how they work better than I do).

Redrobes
02-02-2009, 03:59 PM
Sure, my comments were more directed to GP and this line :-


created in Xara Xtreme, with never touching a raster application

C'mon, its part raster application too.

Edit -- actually Nomadic, your aware of what you find best between the two types which is great. Its the knowing that counts and not dismissing one over the other that is important and knowing when to go 3D or use an effect etc. Its about being aware of your tool set and your comfort with each. Chgowiz asked when to use this or that but the answer is dependent on each person and their ability and comfort with them. I use a significantly different set of tools to everyone else here and all I suggest is that people try out different stuff - at least try a raster and vector app or use the raster and vector parts of one app and try some 3D and a stamping token based tool etc. Each have their own pros and cons and no one app has it all. People who say 'I do everything in xyz app' (which is usually PS actually) are missing out.

Gamerprinter
02-02-2009, 04:37 PM
@Nomadic - I wasn't critizing your process or what best works for you. My disagreement was based on the general state that raster is more real and vector is just faster... what works for you, works for you, I'm not criticizing that. (Vector is faster no matter whether you're creating line art or working with images and photographs)

@Redrobes - I guess I should rephrase that, in my mind a raster application is an image editor (like Photoshop or GIMP) and Xara is not an image editor. Its true it can incorporate raster images in its functionality - and its power to feather, bevel, add transparency in layers is vastly superior than to other applications in its same class.

However, there are many things I can do with Xara, that I couldn't do with other apps like CorelDraw and Micrografx Designer (my original vector app.)

I've also qualified myself saying that I do use Raster apps as need arises or using 3D apps for specific needs. Still Xara is always in my production workflow, though sometimes I use only Xara to create maps.

GP

PS: to avoid pixelization, I always use as high a resolution an image file as I can whether a painted texture or photograph. I try to obtain large format 300 dpi graphics for all my textures when possible.

Nomadic
02-02-2009, 04:48 PM
@Nomadic - I wasn't critizing your process or what best works for you. My disagreement was based on the general state that raster is more real and vector is just faster... what works for you, works for you, I'm not criticizing that. (Vector is faster no matter whether you're creating line art or working with images and photographs)


Yea I know, I was actually trying to avoid someone doing this (why I stated that I personally did it that way). But I am bad about not clarifying that my statement is a personal view. So people still had a bit of trouble understanding that I wasn't saying "raster=real vector=fast" I was saying "for me raster is better at real and vector is better at fast".

Chgowiz
02-03-2009, 09:27 AM
... at least try a ... stamping token based tool

What is that? There have been times when it would have been easier to "stamp" the patterns rather than futz with a layer/mask.

Gamerprinter
02-03-2009, 11:10 AM
Lots of the lower end mapping apps are stamp based tools. Dundjinni is probably the best of that class of application.

GP

Chgowiz
02-03-2009, 12:21 PM
Lots of the lower end mapping apps are stamp based tools. Dundjinni is probably the best of that class of application.

GP

:forehead slap: Duh. I should have known that, as I've used Dundjinni before. I was hoping for something a bit more flexible in terms of output (and something I can use on Linux!)

RobA
02-03-2009, 02:56 PM
@Chgowiz-

Dungeonforge can run under wine (http://www.dungeonmapping.com/df/public_html/index.php?name=Forums&file=viewtopic&t=249) and is a nice little stamp/tile mapping program (though it has its own limitations...)

-Rob A>

Chgowiz
02-03-2009, 03:16 PM
@Chgowiz-

Dungeonforge can run under wine (http://www.dungeonmapping.com/df/public_html/index.php?name=Forums&file=viewtopic&t=249) and is a nice little stamp/tile mapping program (though it has its own limitations...)

-Rob A>

That program is receiving a lot of discussion on the Swords/Wizardry forum the past two days, as they're doing a 3 day megadungeon project. Thank you for telling me that it runs under Wine, now I have Yet Another Program to go check out. *chuckles* May we live in interesting (or at least, mutiple tools options) times.