Drawing a single point fails Metal validation

[levinli303]

I'm using Catalyst version of MetalANGLE, and it seems drawing a single point can fail the Metal validation, the code and error message is as following. When nStars is not 1, it works completely fine.

The stride here is 24, and the three element size are 12 (3 * float), 4 (4 * byte), 4 (1 * float)

[kakashidinho]

hey thanks for reporting,
could you post your sample code snippet here (in text form)? It could be helpful.
cheers,

[levinli303]

a minimum (and messy) snippet for reproduction. it also reproduces on iOS/iOS Simulator

- (void)prepareGL:(CGSize)size {
    const char *vShaderStr =
      "attribute vec3 inPosition;    \n"
      "attribute vec4 inColor;       \n"
      "attribute float inSize;       \n"
      "varying vec4 color;           \n"
      "void main()                   \n"
      "{                             \n"
      "    color = inColor;          \n"
      "    gl_PointSize = inSize;    \n"
      "    gl_Position = vec4(inPosition, 1.0);    \n"
      "}                             \n";
    const char *fShaderStr =
      "precision mediump float;                                   \n"
      "varying vec4 color;                                        \n"
      "void main()                                                \n"
      "{                                                          \n"
      "     gl_FragColor = color;                                 \n"
      "}                                                          \n";

    GLint compiled;
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vShaderStr, NULL);
    glCompileShader(vertexShader);
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &compiled);
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fShaderStr, NULL);
    glCompileShader(fragmentShader);
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &compiled);
    GLint logLength = 0;
    glGetShaderiv(fragmentShader, GL_INFO_LOG_LENGTH, &logLength);
    char* log = malloc(logLength);
    GLsizei charsWritten = 0;
    glGetShaderInfoLog(fragmentShader, logLength, &charsWritten, log);

    GLint linked;
    self.program = glCreateProgram();
    glAttachShader(self.program, vertexShader);
    glAttachShader(self.program, fragmentShader);
    glBindAttribLocation(self.program, 0, "inPosition");
    glBindAttribLocation(self.program, 1, "inSize");
    glBindAttribLocation(self.program, 2, "inColor");
    glLinkProgram(self.program);
    glGetProgramiv(self.program, GL_LINK_STATUS, &linked);
}

- (void)drawGL:(CGSize)size {
    glViewport(0, 0, size.width, size.height);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glUseProgram(self.program);

    static GLuint vboId = 0;

    struct StarVertex
    {
        float position[3];
        float size;
        unsigned char color[4];
        float pad;
    };

    if (vboId == 0)
    {
        struct StarVertex *starCoord = (struct StarVertex *)malloc(sizeof(struct StarVertex) * 1);
        starCoord->position[0] = 0.0f;
        starCoord->position[1] = 0.0f;
        starCoord->position[2] = 0.0f;
        starCoord->color[0] = 255;
        starCoord->color[1] = 0;
        starCoord->color[2] = 0;
        starCoord->color[3] = 255;
        starCoord->size = 20.0f;

        glGenBuffers(1, &vboId);
        glBindBuffer(GL_ARRAY_BUFFER, vboId);
        glBufferData(GL_ARRAY_BUFFER,
                     sizeof(struct StarVertex) * 1,
                     starCoord,
                     GL_STATIC_DRAW);
    }
    else
    {
        glBindBuffer(GL_ARRAY_BUFFER, vboId);
    }

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(struct StarVertex), __offsetof(struct StarVertex, position));
    glVertexAttribPointer(1, 1, GL_FLOAT, GL_FALSE, sizeof(struct StarVertex), __offsetof(struct StarVertex, size));
    glVertexAttribPointer(2, 4, GL_UNSIGNED_BYTE, GL_FALSE, sizeof(struct StarVertex), __offsetof(struct StarVertex, color));

    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glEnableVertexAttribArray(2);

    glDrawArrays(GL_POINTS, 0, 1);

    glDisableVertexAttribArray(0);
    glDisableVertexAttribArray(1);
    glDisableVertexAttribArray(2);
}

the validation does not fail if I replace the 1s in these lines of code with 2.

glBufferData(GL_ARRAY_BUFFER, sizeof(struct StarVertex) * 1, starCoord, GL_STATIC_DRAW);
glDrawArrays(GL_POINTS, 0, 1);