I did forget the widescreen, I'll fix it by making it a little bigger like you're doing xD
Well, the tutorial:
We go to 920101.pac in the adventure folder in the brawl disc, and we open it.
We open a brand new stage (battlefield in this case) to make the stage on it.
In a SSE stage we usually find 2 arc files, the first usually have the bosses/enemies data, the second one is the stage. If we look at a regular stage, we have 2 arcs too, the first one is empty and the second one is the stage.
Well, we must find the data we need from the SSE stage. We have a model previewer so we can see what we're getting. Anyway, in this case, we have only modeldata[0]. There are some models in there, and some animations. We will export this as a brres file.
Don't forget texturedata and scenedata. Without texturedata, we will have a messed up/freezing stage. Scenedata has the lights for our stage. Anyway, we will later see that those lights are not good enough for our stage.
Well, rayquaza is in the first arc file, the enemies one. If interested, just pick the model up, with the textures, and get some animations too, you could need them.
Back to the battlefield pac file, we have to see what's what we want to replace. We'll see that background and sky related modeldatas are all replaceable, so we will import our modeldata[0] over them. If we only replace modeldata[0] once, we will be missing some animations, because only the first of them work. So, this is what we will do as we have a multiple modeldata stage:
We will get the models that don't need animations together with one needing animations. We will delete any other model needing animations, as well as the other animations.
We will import again the brres file over another of the replaceable modeldatas. We will have only 1 model needing textures here. We will delete the others, as well as the unused animations. Keep doing this until we have all the models from our SSE stage brres into our new stage.
Well, the next step would be moving the background down. The lake is the same level as the ground in battlefield, so we have to move down every imported model. In order to do this, be sure you have an auxiliary model in the first position of every modeldata. This auxiliary model is the 'static' model I use, but you can get copies of the poketrainer model in modeldata101 too.
Move them down using animations, only one animation per modeldata. In this case I have lowered it by 120 points. The death limit was -115 I guess, so the ground of the lake stage will be below.
Well, we can now add rayquaza in another unused modeldata, because battlefield has many modeldatas, for sun, moon, sky... Things we don't need. In my case, I've used my imported Deoxys, the rayquaza from the SSE stage, and an imported gyarados. I've made 3 gyarados using 3 different animations, and one of them has a new texture made quickly with paint shop pro 7, making it a shiny pokemon (the red gyarados)
Oh, almost forgot, during this, we have to import the textures from the SSE stage. We can import the whole texturedata brres file we extracted earlier and renaming it to texturedata[1] (texturedata[0] already exists). We need to make the fileid value -1.
We can have some texturedatas, so importing textures manually is no longer needed.
We can have a problem with this (actually I had it). The textures are very space-consuming, much more than 3D models. Having the textures of 2 stages (battlefield and lake) will make the file too big. We need to make textures smaller or decreasing the quality. I had previously made it for the alive rayquaza's stage, so I copy-pasted with no problems. I have seeked which battlefield textures were no longer used by the stage so I could delete them.
And... well, I think this is it. It was really easy to make, the more difficult to me was getting the imported pokemon to work properly, because they have texture issues. Placing them in other modeldatas made them to be black, or having an unestable color. This exact way, they're working perfectly. This is the thing that consumed the most time with making the stage
Well, ask if you have some questions, this should be fine in order to make other stages I guess. The steps would be nearly the same for every sse stage. I forgot to say that I've tested the lightings, even I have edited them. The ones in the final product are not exactly the ones in battlefield, I have deleted the fogs so it looks better for me. I liked the lighting and I barely noticed the light change of the night part of battlefield. I even liked it, so I have left it as is. There's only one more thing I didn't mention, and that's collisions. In SSE stages you can find multiple collision files, so you will have to seek which one fits you more for your stage. In the lake battlefield was not necessary because we're not using any collision from the SSE stage, but other stages will require some attention with them.
This is it xD
Mewtwo, for your alive rayquaza's lake (which looks amazing BTW) can you add the gyarados from your battlefield texture to it? If not can you at least add the red gyrados? The lake of rage was my favorite pokemon fight. Thank you so much.
Sure, I could add them I guess. I wanted to make another pokemon to appear, but I liked my 3 gyarados so I think I will include them too