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Miloslav Číž 2019-06-23 15:36:19 +02:00
parent 729fbe7111
commit e5990afb6d
1 changed files with 14 additions and 1 deletions
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15
small3dlib.h
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@ -1633,6 +1633,18 @@ typedef struct
int16_t minorDiff; int16_t minorDiff;
} S3L_BresenhamState; ///< State of drawing a line with Bresenham algorithm. } S3L_BresenhamState; ///< State of drawing a line with Bresenham algorithm.
/** Serves to accelerate linear interpolation for performance-critical
code. Functions such as S3L_interpolate require division to compute each
interpolated value, while S3L_FastLerpState only requires a division for
the initiation and a shift for retrieving each interpolated value.
S3L_FastLerpState stores a value and a step, both scaled (shifted by
S3L_FAST_LERP_QUALITY) to increase precision. The step is being added to the
value, which achieves the interpolation. This will only be useful for
interpolations in which we need to get the interpolated value in every step.
BEWARE! Shifting a negative value is undefined, so handling shifting of
negative values has to be done cleverly. */
typedef struct typedef struct
{ {
S3L_Unit valueScaled; S3L_Unit valueScaled;
@ -1911,7 +1923,8 @@ void S3L_drawTriangle(
s##SideFLS.valueScaled = 0;\ s##SideFLS.valueScaled = 0;\
if (!down)\ if (!down)\
{\ {\
s##SideFLS.valueScaled = S3L_FRACTIONS_PER_UNIT << S3L_FAST_LERP_QUALITY;\ s##SideFLS.valueScaled =\
S3L_FRACTIONS_PER_UNIT << S3L_FAST_LERP_QUALITY;\
s##SideFLS.stepScaled *= -1;\ s##SideFLS.stepScaled *= -1;\
}\ }\
s##Inc = s##Dx >= 0 ? 1 : -1;\ s##Inc = s##Dx >= 0 ? 1 : -1;\