[Ohrrpgce] OHR - Custom Container Slices (Clipping Paths)

James Paige Bob at hamsterrepublic.com
Sat Oct 19 06:18:08 PDT 2019

I rather like the idea of a new slice type. It seems like I would like to
group multistencils that way anyway even if an extra slice wasn't required.
And simpler code seems like a nice bonus

On Fri, Oct 18, 2019, 11:19 PM Ralph Versteegen <teeemcee at gmail.com> wrote:

> So I have reimplemented stencil slices so that any kind of visible slice
> (excluding Grid, Panel, etc) can act as a stencil, eg text slices. This is
> way better than just using sprites as stencils. Each slice has a "Stencil:
> yes/no" setting. But I want it to be even more general: a whole slice tree
> should be usable as a stencil, not just a single slice. For example if you
> want to draw an NPC in silhouette, and it might be composed of multiple
> sprites for bits of clothing it's wearing. Or use a whole lot of ellipse,
> rect or line slices to make up a stencil.
> There are multiple ways to accomplish that which I can't decide between:
> -Add a new Stencil slice type ("Multistencil" to disambiguate?). The first
> X (configurable) children (and their descendents) are the stencil mask, the
> rest are drawn with the mask
> -Also if we have that new slice type, then we could get rid of the
> "Stencil" bool setting on each slice, and require using that slice type
> instead.  This has the advantage that it cleans up the code, but it
> complicates use since you need an extra slice.
> -Let every slice act like a multistencil by adding an additional setting
> "Add children to stencil: 0+"
> On Mon, 14 Oct 2019 at 19:13, Ralph Versteegen <teeemcee at gmail.com> wrote:
>> Well, you got me motivated, so I started on stencil slices. I did
>> underestimate how easy it would be, but have a working mockup.
>> [image: 22_stencil_slice.gif]
>> Two weeks is a pretty short deadline. As I said, this won't be in Fufluns
>> (I won't be committing these changes to SVN until after the Fufluns branch
>> is made, and we don't want to create branches for stable releases long
>> before the actual release, so that the release candidates are just the
>> nightly builds). I also need to rewrite the implementation to allow all
>> slice kinds to be used both as stencil and as children of a stencil: right
>> now it only works for non-transparent sprites parented to a stencil sprite.
>> Even with all the planning I did I still got it wrong! Planning is no
>> substitute for experimentation.
>> But it's already good enough for your purposes, and I really really want
>> to release Fufluns within two weeks anyway, so maybe you can use it
>> afterall, if you haven't already done it manually.
>> Technical details, since I'm CC'ing to the mailing list:
>> I'd also like to allow multiple sprites/slices to be OR'd into a single
>> stencil, but I'm not sure yet how to do that. Possibly the additional
>> stencils would be children of the main stencil, with a "Combine with parent
>> stencil" setting.
>> Also, I will allow transparent stencils (stencils are actually
>> implemented using the alpha layer/mask, so transparency comes for free).
>> I'm implementing stencils in a way that will allow a straight-forward
>> hardware accelerated implementation when we add that, although the initial
>> implementation is with software and could work any way I want.
>> The funny thing is OpenGL has something called "stencils" but they are
>> useless for my purposes since there's no way to set the stencil mask to a
>> bitmap; if you want to draw something in the mask you have to split it into
>> triangles. So I'm forced to instead implement stencils using the alpha
>> layer and a framebuffer (FBO). Also I don't want to use OpenGL directly if
>> I can avoid it, but go through SDL 2 for rendering, since it has separate
>> backends for DirectX9, OpenGL ES 2.0, OpenGL, etc. SDL2 exposes FBOs as
>> render-target textures, and it allows custom blend modes, but it doesn't
>> expose stencils or depth buffers. (Note I don't have real OpenGL
>> experience, just reading a bunch of docs over the years.)
>> OpenGL stencils would not allow transparency (and since OpenGL is just
>> exposing a feature of the render output units (ROP) on GPUs I assume all
>> other graphics APIs have the same limitation).
>> On Sat, 12 Oct 2019 at 03:33, Matt Edson <colesloth at gmail.com> wrote:
>>> Haha, in like two weeks. I'm already going to plan on doing it manually.
>>> No need in escalating anything on my account. I was just seeing if it was
>>> available already or if it was something easy as some of my requests are,
>>> like when James did Shrink to Center, which was amazing.
>>> On Fri, Oct 11, 2019 at 10:14 AM Ralph Versteegen <teeemcee at gmail.com>
>>> wrote:
>>>> This is something I've wanted to implement for years! I'm sure people
>>>> would find interesting uses of it, such as drawing reflections.
>>>> It's actually not hard to implement, and the reason I haven't was
>>>> because I wasn't sure exactly how to go about it (there are a lot of ways
>>>> it could work) so that it could be feasibly reimplemented when we switch to
>>>> hardware-accelerated rendering, and in particular, when using SDL 2 for
>>>> rendering, which is far more restrictive than using OpenGL/DirectX/etc
>>>> directly. But a couple months ago I spent most of a day reading the SDL 2
>>>> graphics drivers source code, OpenGL docs, etc, to figure this out and
>>>> confirmed that this should be possible to implement in SDL2 by using a
>>>> destination texture alpha channel and custom blend mode. That means I can
>>>> implement it in our current software renderer too.
>>>> I'm certainly not going to do this before Fufluns is released, and I
>>>> don't know when exactly I'll get to it, since there are so many different
>>>> things I want to do after Fufluns is released. When would you need it by?
>>>> On Fri, 11 Oct 2019 at 14:43, Matt Edson <colesloth at gmail.com> wrote:
>>>>> No worries. I wanted to check before I did anything. Thanks!
>>>>> On Thu, Oct 10, 2019 at 9:40 PM James Paige <Bob at hamsterrepublic.com>
>>>>> wrote:
>>>>>> That would be so cool!
>>>>>> We don't have a clipping bitmap slice, although that would be a
>>>>>> fantastic feature which I would love to add someday in the future. I have
>>>>>> no idea how difficult it would be to implement, so I couldn't guess how
>>>>>> long it will take.
>>>>>> For now, you best bet is to just animate it as a bunch of sprites
>>>>>> On Thu, Oct 10, 2019 at 5:23 PM Matt Edson <colesloth at gmail.com>
>>>>>> wrote:
>>>>>>> Hey guys...
>>>>>>> So I'm getting ready to move on to the next area for Axe Cop and I
>>>>>>> do fancy intros for all of the levels. I had this idea today where I could
>>>>>>> do a clipping mask of the word WATER in a font that I figure out and I was
>>>>>>> kind of hoping to make a clipping mask of it and then I was going to ascend
>>>>>>> a graphic of running water through it so it would look like the word Water
>>>>>>> was filling up with water to fill it up and it'd look really cool.
>>>>>>> I opened the container area of the slice editor and it seems I can
>>>>>>> only do rectangles. Is there any way to do this idea/and/or is there an
>>>>>>> easy way to implement custom containers for this type of thing or is it one
>>>>>>> of those things I should just brainstorm a new idea for the title card of
>>>>>>> the level?
>>>>>>> This idea worked well just because the stage is about raising and
>>>>>>> lowering the levels of water. I could draw all of the frames manually but I
>>>>>>> try to be the most economic with my resources and that'd be a ton of new
>>>>>>> giant sprites.
>>>>>>> Let me know! Thanks dudes!
>>>>>> _______________________________________________
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