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Fix segfault for large bases in perlin noise #36

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Fix segfault for large bases in perlin noise #36

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8cd586e
Fix segfault for large bases in perlin noise
mwshinn Jan 4, 2022
bf25910
Throw error for invalid bases
mwshinn Feb 20, 2022
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42 changes: 27 additions & 15 deletions _perlin.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@ noise1(float x, const int repeat, const int base)
float fx;
int i = (int)floorf(x) % repeat;
int ii = (i + 1) % repeat;
i = (i & 255) + base;
ii = (ii & 255) + base;
i = ((i + base) & 255);
ii = ((ii + base) & 255);

x -= floorf(x);
fx = x*x*x * (x * (x * 6 - 15) + 10);
Expand All @@ -52,6 +52,10 @@ py_noise1(PyObject *self, PyObject *args, PyObject *kwargs)
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "f|iffii:noise1", kwlist,
&x, &octaves, &persistence, &lacunarity, &repeat, &base))
return NULL;
if (base < 0 || base > 255) {
PyErr_SetString(PyExc_ValueError, "Base must be between 0 and 255");
return NULL;
}

if (octaves == 1) {
// Single octave, return simple noise
Expand Down Expand Up @@ -92,10 +96,10 @@ noise2(float x, float y, const float repeatx, const float repeaty, const int bas
int j = (int)floorf(fmodf(y, repeaty));
int ii = (int)fmodf(i + 1, repeatx);
int jj = (int)fmodf(j + 1, repeaty);
i = (i & 255) + base;
j = (j & 255) + base;
ii = (ii & 255) + base;
jj = (jj & 255) + base;
i = ((i + base) & 255);
j = ((j + base) & 255);
ii = ((ii + base) & 255);
jj = ((jj + base) & 255);

x -= floorf(x); y -= floorf(y);
fx = x*x*x * (x * (x * 6 - 15) + 10);
Expand Down Expand Up @@ -130,6 +134,10 @@ py_noise2(PyObject *self, PyObject *args, PyObject *kwargs)
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "ff|iffffi:noise2", kwlist,
&x, &y, &octaves, &persistence, &lacunarity, &repeatx, &repeaty, &base))
return NULL;
if (base < 0 || base > 255) {
PyErr_SetString(PyExc_ValueError, "Base must be between 0 and 255");
return NULL;
}

if (octaves == 1) {
// Single octave, return simple noise
Expand Down Expand Up @@ -173,12 +181,12 @@ noise3(float x, float y, float z, const int repeatx, const int repeaty, const in
int ii = (int)fmodf(i + 1, repeatx);
int jj = (int)fmodf(j + 1, repeaty);
int kk = (int)fmodf(k + 1, repeatz);
i = (i & 255) + base;
j = (j & 255) + base;
k = (k & 255) + base;
ii = (ii & 255) + base;
jj = (jj & 255) + base;
kk = (kk & 255) + base;
i = ((i + base) & 255);
j = ((j + base) & 255);
k = ((k + base) & 255);
ii = ((ii + base) & 255);
jj = ((jj + base) & 255);
kk = ((kk + base) & 255);

@flomnes flomnes Feb 17, 2022

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From what I understand you're capping the result to 255. This can be misleading to the user since it's a hidden operation : the user could expect different results with larger values for base and not get them.

I'd recommend throwing an error or at least a warning.

x -= floorf(x); y -= floorf(y); z -= floorf(z);
fx = x*x*x * (x * (x * 6 - 15) + 10);
Expand Down Expand Up @@ -220,6 +228,10 @@ py_noise3(PyObject *self, PyObject *args, PyObject *kwargs)
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "fff|iffiiii:noise3", kwlist,
&x, &y, &z, &octaves, &persistence, &lacunarity, &repeatx, &repeaty, &repeatz, &base))
return NULL;
if (base < 0 || base > 255) {
PyErr_SetString(PyExc_ValueError, "Base must be between 0 and 255");
return NULL;
}

if (octaves == 1) {
// Single octave, return simple noise
Expand Down Expand Up @@ -248,14 +260,14 @@ py_noise3(PyObject *self, PyObject *args, PyObject *kwargs)

static PyMethodDef perlin_functions[] = {
{"noise1", (PyCFunction) py_noise1, METH_VARARGS | METH_KEYWORDS,
"noise1(x, octaves=1, persistence=0.5, lacunarity=2.0, repeat=1024, base=0.0)\n\n"
"noise1(x, octaves=1, persistence=0.5, lacunarity=2.0, repeat=1024, base=0)\n\n"
"1 dimensional perlin improved noise function (see noise3 for more info)"},
{"noise2", (PyCFunction) py_noise2, METH_VARARGS | METH_KEYWORDS,
"noise2(x, y, octaves=1, persistence=0.5, lacunarity=2.0, repeatx=1024, repeaty=1024, base=0.0)\n\n"
"noise2(x, y, octaves=1, persistence=0.5, lacunarity=2.0, repeatx=1024, repeaty=1024, base=0)\n\n"
"2 dimensional perlin improved noise function (see noise3 for more info)"},
{"noise3", (PyCFunction) py_noise3, METH_VARARGS | METH_KEYWORDS,
"noise3(x, y, z, octaves=1, persistence=0.5, lacunarity=2.0, "
"repeatx=1024, repeaty=1024, repeatz=1024, base=0.0)\n\n"
"repeatx=1024, repeaty=1024, repeatz=1024, base=0)\n\n"
"return perlin \"improved\" noise value for specified coordinate\n\n"
"octaves -- specifies the number of passes for generating fBm noise,\n"
"defaults to 1 (simple noise).\n\n"
Expand Down