Billboards - alpha testing failing on just *some* textures

[MontyOnTheRun]

Hello all.
Thank you for the space and for the hard work!

I've been trying to port my game engine to the Gamecube and Wii, but somehow I can't seem to render my billboards without the texture border.
What's odd is that, for bitmapped fonts and some other 2D elements, it renders fine!



If I try to load some texture at the same time I was loading the fonts, it will work fine. If I use the same code at some other time, it will render the borders (It should be noted that I'm loading my textures from my own binary blob instead of using TPLs).

My code is also heavily based on neheGX.

My initialization:

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VIDEO_Init();
    
#ifdef GX
    PAD_Init();
#endif

#ifdef WII
    WPAD_Init();
#endif

    rmode = VIDEO_GetPreferredMode(NULL);

    gpfifo = memalign(32,DEFAULT_FIFO_SIZE);
    memset(gpfifo,0,DEFAULT_FIFO_SIZE);

    frameBuffer[0] = SYS_AllocateFramebuffer(rmode);
    frameBuffer[1] = SYS_AllocateFramebuffer(rmode);

    VIDEO_Configure(rmode);
    VIDEO_SetNextFramebuffer(frameBuffer[fb]);
    VIDEO_Flush();
    VIDEO_WaitVSync();
    if(rmode->viTVMode&VI_NON_INTERLACE) VIDEO_WaitVSync();

    fb ^= 1;

    GX_Init(gpfifo,DEFAULT_FIFO_SIZE);

    GX_SetCopyClear(background, 0x00ffffff);

    GX_SetViewport(0,0,rmode->fbWidth,rmode->efbHeight,0,1);
    yscale = GX_GetYScaleFactor(rmode->efbHeight,rmode->xfbHeight);
    xfbHeight = GX_SetDispCopyYScale(yscale);
    GX_SetScissor(0,0,rmode->fbWidth,rmode->efbHeight);
    GX_SetDispCopySrc(0,0,rmode->fbWidth,rmode->efbHeight);
    GX_SetDispCopyDst(rmode->fbWidth,xfbHeight);
    GX_SetCopyFilter(rmode->aa,rmode->sample_pattern,GX_TRUE,rmode->vfilter);
    GX_SetFieldMode(rmode->field_rendering,((rmode->viHeight==2*rmode->xfbHeight)?GX_ENABLE:GX_DISABLE));

    if (rmode->aa) {
        GX_SetPixelFmt(GX_PF_RGB565_Z16, GX_ZC_LINEAR);
    } else {
        GX_SetPixelFmt(GX_PF_RGB8_Z24, GX_ZC_LINEAR);
    }

    GX_SetCullMode(GX_CULL_NONE);
    GX_CopyDisp(frameBuffer[fb],GX_TRUE);
    GX_SetDispCopyGamma(GX_GM_1_0);

    GX_ClearVtxDesc();
    GX_SetVtxDesc(GX_VA_POS, GX_DIRECT);
    GX_SetVtxDesc(GX_VA_CLR0, GX_DIRECT);
    GX_SetVtxDesc(GX_VA_TEX0, GX_DIRECT);

    GX_SetVtxAttrFmt(GX_VTXFMT0, GX_VA_POS, GX_POS_XYZ, GX_F32, 0);
    GX_SetVtxAttrFmt(GX_VTXFMT0, GX_VA_TEX0, GX_TEX_ST, GX_F32, 0);
    GX_SetVtxAttrFmt(GX_VTXFMT0, GX_VA_CLR0, GX_CLR_RGBA, GX_RGB8, 0);

    GX_SetTexCoordGen(GX_TEXCOORD0, GX_TG_MTX2x4, GX_TG_TEX0, GX_IDENTITY);

    GX_SetTevOp(GX_TEVSTAGE0,GX_MODULATE);
    GX_SetTevOrder(GX_TEVSTAGE0, GX_TEXCOORD0, GX_TEXMAP0, GX_COLOR0A0);

    GX_SetNumTexGens(1);
    GX_SetNumChans(1);
    GX_InvVtxCache();
    GX_InvalidateTexAll();

    GX_SetAlphaUpdate(GX_TRUE);
    GX_SetAlphaCompare(GX_GREATER,0,GX_AOP_AND,GX_ALWAYS,0);

    memset(&whiteTextureData[0], 0xFF, 32 * 32 * 4);

    GX_InitTexObj(&whiteTextureObj, &whiteTextureData[0], 32, 32, GX_TF_RGBA8, GX_REPEAT, GX_REPEAT, GX_FALSE);
    

(yes, I'm using a white texture for plotting solid shapes. I'm not entirely sure how this could be better performed)

Of course, at some point the perspective is also set, but given how the billboard renders corectly (if we ignore the border, which is RGBA #00000000, BTW), I don't see this as an issue.

How am I loading my textures? Besides all the memory allocation (properly aligned) and stuff, once I have my raw RGBA bitmap loaded (and taking into consideration the texture block arrangement), I issue:

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    DCFlushRange(bitmap->data, bitmap->width * bitmap->height * 4);
    GX_InitTexObj(bitmap->nativeBuffer, bitmap->data, bitmap->width, bitmap->height, GX_TF_RGBA8, GX_REPEAT, GX_REPEAT, GX_FALSE);

And finally, the binding:

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GX_LoadTexObj(bitmap->nativeBuffer, GX_TEXMAP0);

The polygon drawing code is very straightforward:

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    GX_Begin(GX_QUADS, GX_VTXFMT0, 4);	

    GX_Position3f32(vx1, vy1, vz1);
    GX_Color3f32(1,1,1);
    GX_TexCoord2f32(u1, v1);

    GX_Position3f32( vx2, vy2, vz2);
    GX_Color3f32(1,1,1);
    GX_TexCoord2f32(u2, v2);

    GX_Position3f32(vx4, vy4, vz4);
    GX_Color3f32(1,1,1);
    GX_TexCoord2f32(u4, v4);

    GX_Position3f32( vx3, vy3, vz3);
    GX_Color3f32(1,1,1);
    GX_TexCoord2f32(u3, v3);

    GX_End();

This code is a port from an OpenGL version (written for the N64's LibDragon and NDS's devkit GL wrapper, but also supporting PPC Macs and newer stuff), from what was originally a software rendering engine (thank you guys for allowing me to support the GBA on that!)

I'm on my wit's end. I hope you guys could help me figuring out what I'm missing, please?

[MontyOnTheRun]

Fixed!



Turns out I needed to issue GX_SetZCompLoc(GX_FALSE);
Heck, the docs even mention my case as an example!