[Scummvm-tracker] [ScummVM :: Bugs] #15272: TINY: triangle fan produces less triangles than expected?

[ScummVM :: Bugs]

#15272: TINY: triangle fan produces less triangles than expected?
------------------------+----------------------
Reporter:  neuromancer  |      Owner:  (none)
    Type:  defect       |     Status:  new
Priority:  normal       |  Component:  Graphics
 Version:               |   Keywords:  tinygl
    Game:               |
------------------------+----------------------
 TGL_TRIANGLE_FAN seems to produce less triangles than expected. Check the
 screenshots associated, where similar code is for TinyGL and OpenGL
 implementation. The code is basically this one:

 {{{
 void TinyGLRenderer::drawCelestialBody(Math::Vector3d position, float
 radius, byte color) {
     uint8 r1, g1, b1, r2, g2, b2;
     byte *stipple = nullptr;
     getRGBAt(color, 0, r1, g1, b1, r2, g2, b2, stipple);

     int triangleAmount = 20;
     float twicePi = (float)(2.0 * M_PI);
     ...

     tglDisable(TGL_DEPTH_TEST);
     tglDepthMask(TGL_FALSE);

     setStippleData(stipple);
     useColor(r1, g1, b1);

     tglEnableClientState(TGL_VERTEX_ARRAY);
     copyToVertexArray(0, position);
     float adj = 1.25; // Perspective correction

     for(int i = 0; i <= triangleAmount; i++) {
         copyToVertexArray(i + 1,
             Math::Vector3d(position.x(), position.y() + (radius * cos(i *
 twicePi / triangleAmount)),
                         position.z() + (adj * radius * sin(i * twicePi /
 triangleAmount)))
         );
     }

     tglVertexPointer(3, TGL_FLOAT, 0, _verts);
     tglDrawArrays(TGL_TRIANGLE_FAN, 0, triangleAmount + 2);
     tglDisableClientState(TGL_VERTEX_ARRAY);
 }
 }}}

 I'm also seeing a bunch of sanitizer warning/errors when rendering this,
 perhaps they are related:

 {{{

 graphics/tinygl/ztriangle.cpp:418:19: runtime error: left shift of
 negative value -5
 graphics/tinygl/ztriangle.cpp:362:16: runtime error: left shift of
 negative value -10
 graphics/tinygl/clip.cpp:251:58: runtime error: signed integer overflow:
 -2147483648 - 43 cannot be represented in type 'int'
 graphics/tinygl/clip.cpp:252:24: runtime error: signed integer overflow:
 -2147483648 - 185 cannot be represented in type 'int'
 graphics/tinygl/ztriangle.cpp:212:23: runtime error: signed integer
 overflow: 185 - -2147483648 cannot be represented in type 'int'
 graphics/tinygl/ztriangle.cpp:213:23: runtime error: signed integer
 overflow: 32 - -2147483648 cannot be represented in type 'int'
 graphics/tinygl/ztriangle.cpp:215:23: runtime error: signed integer
 overflow: 185 - -2147483648 cannot be represented in type 'int'
 graphics/tinygl/ztriangle.cpp:216:23: runtime error: signed integer
 overflow: 43 - -2147483648 cannot be represented in type 'int'
 graphics/tinygl/ztriangle.cpp:362:16: runtime error: left shift of
 negative value -102
 graphics/tinygl/ztriangle.cpp:418:19: runtime error: left shift of
 negative value -102
 graphics/tinygl/clip.cpp:251:27: runtime error: signed integer overflow:
 -2147483648 - 159 cannot be represented in type 'int'
 graphics/tinygl/clip.cpp:252:55: runtime error: signed integer overflow:
 -2147483648 - 32 cannot be represented in type 'int'
 }}}
-- 
Ticket URL: <https://bugs.scummvm.org/ticket/15272>
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