Red Mountain, particularly its first and third acts, was reworked in SADX to a more noticeable degree than other stages. Acts 1 and 3 have new textures and at least one new texture is higher resolution than the textures used in the Dreamcast level. Many people seem to genuinely prefer the SADX redesign, and perhaps Acts 1/3 are not the worst when it comes to SADX downgrades – unlike Act 2, which is a downgrade from the original in every aspect. However, even Acts 1/3 have some noticeable changes that can be seen as inferior to the Dreamcast version.
From a quick look it may seem that the SADX version of Red Mountain has higher resolution textures than its Dreamcast counterpart, but that isn’t entirely true. If you compare the textures between the Gamecube and Dreamcast versions, you’ll notice that there’s only one texture in the Gamecube/PC version that is 512×512, and the rest of the textures are mostly the same resolution as on the Dreamcast or lower. SADX replaces one 128×128 texture with a 256×256 one, but four 256×256 textures were also replaced with 16×16 textures in SADX. In addition, there are two extra textures on the Gamecube/PC.
Despite the increased total number of textures, the variety of them suffered a little bit. In the Dreamcast version there are three mountain textures: one used before the zipline (
ai256_iwa31), one used after the zipline (
ai256_iwa26) and one used near the end of the stage (
d128side8a). In SADX there are only two: one before (
ai256_iwa28) and one after the zipline (
d128side8a). Both of them are less varied/colorful than their Dreamcast counterparts, and only the second texture is higher resolution than the Dreamcast version (and the only texture that is 512×512):
In Act 1 in particular, something happened to several textures in SADX: their resolution was reduced to 16×16, and their hue was shifted to make them blue. Two other textures were not shrunk but still received the blue coloration. These textures appear to be unused, which means that the SADX version of the level actually uses less textures than its Dreamcast counterpart.
Of course this is barely relevant without comparing the actual look of the level ingame, so let’s compare the start location between versions. The grass textures look more detailed in SADX, but the overall look is less colorful and the lighting is darker and less complex if you look at the badniks and objects:
The Dreamcast version conveys a more coherent impression of the “volcanic” nature of the area:
The ports have transparency and material color issues with cloud layers. In the Dreamcast version there are two layers of white clouds that move with different speeds, creating a “parallax” effect. This effect is barely noticeable in the Gamecube version (and the clouds move in a different direction), and completely gone in the PC version, which also gives the clouds a dirty grey color because of unnecessary processing of material colors:
All versions of SADX are also struggling with draw distance in this level, and the clouds don’t go far enough. They are also placed lower in SADX. In addition, the PC version has thick purple fog, which conflicts with the atmosphere because the color is a bit out of place:
The clouds not reaching far enough is particularly an issue in Knuckles’ level, where the exposed bottom part of the mountains looks like a black void. It becomes a noticeable problem when you go to the lower segments of the level:
The clouds also look less impressive from above in the PC version (which all the later console ports are based on), you can also see how the Dreamcast version of the level is generally brighter and more colorful than its SADX counterpart. Some levels (Big’s Ice Cap for example) changed from night to day, for this one you could say it changed from summer to late fall (Left: Dreamcast, Middle: Gamecube, Right: PC):
A recurrent problem with the ports is loss of detail in character lighting. The characters in the Dreamcast version often had palettes that matched the level’s theme, or had an otherwise unique effect. For example, in Red Mountain Act 1 Sonic is illuminated from one side with a yellow specular light. Although the Gamecube version had a character lighting system that could’ve been as capable as the Dreamcast version, the characters seldom have noticeable differences from the ordinary glossy look. The PC version’s character lighting is even worse than on the Gamecube because it disregards half of the coloration values left over from the console port.
In many levels in the Dreamcast version level geometry loaded in once you got close enough, much like objects in all versions of the game. In some cases, such as Windy Valley Act 3, the pop-in was noticeable enough to get annoying. SADX increases draw distance for some levels and changes the pop-in to work in a different way: instead of drawing the entire level geometry piece when the camera is within its range, the game only shows parts of it gradually as the camera gets closer. This can work well in combination with fog, but Red Mountain ended up getting problems that the Dreamcast version didn’t have. Here’s a video comparison of level geometry pop-in between versions. You can clearly see that the Dreamcast has no pop-in in this area, while SADX has a strange looking mountain partially showing and hiding itself in the background:
This becomes noticeable enough once you climb up the mountain. This particular instance of pop-in was even reported as a bug with SADX mods!
The Dreamcast version doesn’t have this problem because it doesn’t draw the problematic level pieces at this distance. Also note the much better lighting and the subtle white fog that enhances the look of distant mountains.
The last area in Act 1 has some lighting detail removed. Note how the subtle glare is missing on the machinery and the surroundings:
Let’s end the discussion of Act 1 with a texture quality comparison. This is what the sky looks like in all 3 versions, the PC version again being the worst of all:
Act 2 is missing many lighting detail in SADX, although some vertex colors were added. The Dreamcast version’s lighting affected both the objects and the environment around them. Objects such as skulls, gravestones, boxes, badniks etc. are no longer tinted red on the Gamecube. Note how even the rings have some faint red glow in the Dreamcast version. The lighting system used in SADX does not allow for this kind of ambience:
The level itself has also largely lost its “red” theme, with the SADX version being darker and less colorful overall:
The following screenshot demonstrates how the loss of lighting affects the ambience of the level. Note how the skull becomes less distinguishable from the wall with each port:
The “redness” of the original level also worked quite well in motion. Here is a comparison of a section with rocks falling into lava, which has lost quite a bit of ambience in SADX:
In the section outside the caves, the skybox is stretched and the clouds don’t go far enough:
One major change about the SADX redesign of Red Mountain is the new lava texture, which looks more detailed. The lava is less bright in the PC version because of unnecessary processing of material colors.
Red Mountain is one of the bigger redesigns in SADX, both due to its texture changes and different lighting. To get the original lighting back you can install the Lantern Engine mod, and to fix other downgrades you can use the Dreamcast Conversion mod. If you prefer the SADX redesign of the level, you can turn off Red Mountain in Dreamcast Conversion config in the Mod Loader and use the Gamecube Project mod. For more, check out the section about fixing the PC version of SADX.