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Fix z-divide

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This commit is contained in:
Miloslav Číž 2019-05-16 22:02:50 +02:00
parent 0fde459ca7
commit e97ea1c5cc
2 changed files with 26 additions and 2 deletions
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15
s3l.h
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@ -323,7 +323,7 @@ typedef S3L_Unit S3L_Mat4[4][4]; /**< 4x4 matrix, used mostly for 3D
transforms. The indexing is this: transforms. The indexing is this:
matrix[column][row]. */ matrix[column][row]. */
#define S3L_writeMat4(m)\ #define S3L_writeMat4(m)\
printf("Mat4:\n %d %d %d %d\n %d %d %d %d\n %d %d %d %d\n %d %d %d %d\n"\ printfi"Mat4:\n %d %d %d %d\n %d %d %d %d\n %d %d %d %d\n %d %d %d %d\n"\
,(m)[0][0],(m)[1][0],(m)[2][0],(m)[3][0],\ ,(m)[0][0],(m)[1][0],(m)[2][0],(m)[3][0],\
(m)[0][1],(m)[1][1],(m)[2][1],(m)[3][1],\ (m)[0][1],(m)[1][1],(m)[2][1],(m)[3][1],\
(m)[0][2],(m)[1][2],(m)[2][2],(m)[3][2],\ (m)[0][2],(m)[1][2],(m)[2][2],(m)[3][2],\
@ -1356,7 +1356,14 @@ void S3L_makeCameraMatrix(S3L_Transform3D cameraTransform, S3L_Mat4 *m)
static inline void S3L_perspectiveDivide(S3L_Vec4 *vector, static inline void S3L_perspectiveDivide(S3L_Vec4 *vector,
S3L_Unit focalLength) S3L_Unit focalLength)
{ {
S3L_Unit divisor = S3L_nonZero(vector->z); S3L_Unit divisor = vector->z > 0 ? vector->z : (-1 * (vector->z - 1));
/* ^ This has two purposes:
1. Prevent division by zero.
2. Prevent a "rapid flip" of the vertex, e.g.: having a vertex
[100,0,0.1] z-divides it to [1000,0], but when it shift a short
distance to [100,0,-0.1], it z-divides to [-1000,0], rapidly flipping
from right to the left. */
vector->x = (vector->x * focalLength) / divisor; vector->x = (vector->x * focalLength) / divisor;
vector->y = (vector->y * focalLength) / divisor; vector->y = (vector->y * focalLength) / divisor;
@ -1398,8 +1405,12 @@ void S3L_drawModelIndexed(
transformed##n.x = pointModel.x;\ transformed##n.x = pointModel.x;\
transformed##n.y = pointModel.y;\ transformed##n.y = pointModel.y;\
transformed##n.z = pointModel.z;\ transformed##n.z = pointModel.z;\
transformed##n.w = S3L_FRACTIONS_PER_UNIT;\
S3L_perspectiveDivide(&transformed##n,camera->focalLength); S3L_perspectiveDivide(&transformed##n,camera->focalLength);
/* TODO: maybe create an option that would use a cache here to not
transform the same point twice? */
project(0) project(0)
project(1) project(1)
project(2) project(2)

13
testSDL.c
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@ -127,6 +127,18 @@ S3L_DrawConfig conf;
void draw() void draw()
{ {
/*
if (frame % 128 == 0)
{
printf("frame: %d\n",frame);
printf("camera:\n");
printf(" translation: ");
S3L_writeVec4(camera.transform.translation);
printf(" rotation: ");
S3L_writeVec4(camera.transform.rotation);
}
*/
offScreenPixels = 0; offScreenPixels = 0;
clearScreen(); clearScreen();
@ -198,6 +210,7 @@ int main()
S3L_initCamera(&camera); S3L_initCamera(&camera);
camera.transform.translation.z = -S3L_FRACTIONS_PER_UNIT * 2; camera.transform.translation.z = -S3L_FRACTIONS_PER_UNIT * 2;
// camera.transform.translation.x = S3L_FRACTIONS_PER_UNIT; // camera.transform.translation.x = S3L_FRACTIONS_PER_UNIT;
// camera.transform.translation.y = S3L_FRACTIONS_PER_UNIT; // camera.transform.translation.y = S3L_FRACTIONS_PER_UNIT;